Design Decisions

Aright, now that I've talked about box, line and lane I can move on.

Defaults

There's sort of a default configuration as far as what's considered good stance.  You want to have your weight evenly(ish) distributed between both legs so that they can both move quickly.  You want to make sure that you don't cross planes; IE, you aren't sitting with your feet parallel or one directly in front of the other as this makes it more difficult to either evade backwards or side to side since you now have to move through your own body.  A good default stance for your weapons is to have them in front of your body so that they are directly in front of your arms, thereby absorbing any arm snipes.  For your torso it's a good idea generally to be standing upright (IE, not hunched over) and with the torso slightly angled (as this reduces the area a person can easily stab).  Generally speaking have your knees a little bit bent and your elbows a little bit bent is useful as well.  If you know me on facebook here's an image of me in a vaguely neutral stance (my left arm is a bit high, providing a potential shot at my arm).  If not I'm sure that somewhere on the internet is a picture of someone in a default stance.  If anyone goes to the effort to look that up please drop it in the comments.  Any alteration to this basic stance has consequences.  Changing this stance isn't inherently good or bad so long as you're aware of what those consequences are and fortunately for you, this post is all about getting into those.

Potential Energy

Any joint in your body can either by bent or can be extended.  If a joint is bent then it's storing potential energy, this means that when you take a shot and extend that joint you'll get a sudden surge of speed by burning that stored energy.  You can either use this to increase the speed at which you throw, the angle on your shot, or the distance that it travels.  If a joint is extended then the speed at which you can generate one short motion is enhanced.  That's vague, so let me break that down a bit with an example.

Suppose the basic stance above, left foot and hand forward, right foot and hand back, fighting single blue.  In this position your left hand is further forward which means that shots thrown from that hand will travel the shortest distance before hitting a viable target.  This also means that with the elbow joint partially bent you'll be able to generate a snap shot that goes very very fast.  The right hand by contrast won't be able to throw shots as quickly as the distance between it's "neutral" or guard position and its strike is a much greater distance then between your left hand and it's target zones.  This means that if you want to take a bunch of quick shots, fighting with your sword in your left hand makes a lot more sense.  That back hand still has some advantages though.  The back hand is coiled up, because your shoulder is back.  This means that when you throw with that hand (caveats: [because of Bogan] when your feet don't move and without bending over/giving up a shot on your back) you actually have more reach and can hit targets that are farther away.  Additionally the shot itself will be thrown with more velocity making it harder to block or counter.  Finally, having your back hand throw a swing gives you access to more angles and more potential shots because you have time to change the direction of the shot as it's being thrown.  This is an example of coiling up JUST your shoulder and elbow.  You can also coil your legs allowing you to take deeper, longer steps by putting more bend into your knees and ankles or you can leave them uncoiled to take short fast steps.  You can also coil your body by compressing yourself and turning in one direction; when you throw a shot to the opposite direction as you coiled you then gain that additional potential energy.

Front Hand vs Back Hand

So, why choose one hand over the other?

Choose the forward hand as your sword hand if you think that you're faster then your opponent, or you tend to be a more technical fighter.  Having the extra speed to throw shots with will mean that you can hit your enemy before they hit you, often either taking out their arm or going straight in for a body shot as soon as they get into range.  This is also an excellent tactic for hand-matching, wherein you try to beat their sword with your sword by landing a block into a quick counter blow.  Additionally with a weapon in your opponents face they may hesitate to go for torso swings, instead opting to fight the weapon in front of them instead of you.  That having been said, it is my that the downside of this stance is that with your weapon all the way extended in front of you makes it easier for your opponent to land torso swings if they can get past your guard.  Also, with a weapon in front of you if they do somehow break your guard you have very little time to react.

Choose the back hand as your sword hand if you find yourself relying more on trick shots and deception.  Fighting with the hand back will allow you to throw more shots at more angles which will make your attacks hard to predict and as a bonus, since they'll move faster when you do throw them they'll be even harder to throw counters against.  A hand held back is an excellent chance to use a 3-split (under 4 way) which will mean your opponent dies if they got your swing wrong just once.  Since people sometimes fight a sword rather then a person, having your sword back will cause them to have to swing far away from their own box/guard which leaves them more vulnerable to a counter strike, especially if you have better body mechanics.  That having been said it's my opinion that fighting this way makes it much easier to snipe your other hand.  If you know that swing is coming and you're in a single blue duel, you may be able to get a more valuable counter strike (sword arm or torso for off hand), but on the other hand you may just be down a limb.

Torso

You can modify the position of your torso on basically two axis.  You can be standing up tall or leaned over modifying your vertical axis and you can be turned or flat, rotating on your horizontal axis.  You can also lean forward or backwards, though generally it's a good idea to be in a neutral position.  The only reason I can think to lean forward or backwards would be to try to feint with some part of your body.  Doing this gives you nothing and generates openings for your opponent.

Dropping low (or just being short) will give you access to angles that aren't swung at all the time, often allowing you to pop shots up underneath a person's guard, whether that's a shield or just a sword, making torso swings (especially around the hips/stomach) much easier to land.  Dropping low however does make it so that your opponent will have a much easier time throwing an overhand vertical wrap shot on you, thereby bypassing the top of a shield or other guard.

Standing tall (or just being tall) will make the overhand vertical wrap shot a much easier shot to throw.  Additionally this allows you to work over a person's weapon, often sniping their sword arm, or working around a polearm's guard.  The disadvantage of standing tall is that it takes some spring out of your legs and the result is that it much easier to have someone hit them.  Additionally, depending on the differential between their relative and your height you may expose yourself to shots to your hips and torso.

Legs

While a good neutral stance has your weight distributed evenly between both legs you can of course choose to put more weight in your front or back foot.  Putting more weight on your back foot will allow you to get your front foot out of the way faster when avoiding a leg sweep.  Putting more weight on your forward foot will mean that you can step forward a bit faster.

Do what works

These are your design decisions.  Some things are innate, like how flexible, how fast, or how tall you are and will effect what decisions you can/should make.  Within those parameters though it's up to you to decide exactly what decisions you want to make, whether it's tuning things to be an in close aggressive fighter who works low angles, or a long range person who sits defensively and waits for the other person to make a mistake.  There isn't necessarily a right or wrong set of design decisions as it all eventually boils down to personal choice.  That having been said, contextually, you can make better or worse decisions.  Against a person who is already taller then you, doing anything to make it easier for them to hit you in the back is probably detrimental.

Flow

The thing about design decisions is that they aren't static.  You can change the position of each part of your body moment to moment as the fight ebbs and flows.  ...and so can your opponent.  What this means is that it's important for you to be aware of what design decisions you're making moment to moment, and as you improve, being able to track what design decisions your opponent is making moment to moment.  If they suddenly got tall, they may be about to take a wrap shot, if they suddenly got low, expect that you may need to guard your hips/torso.  As much of fighting it's not so much about making the "right" call, as it is about being aware of what's going on.  From there it's all up to your own judgement which is something that you can hone over time.