Oh, well. Going back to what both you and LittleFox have told me, I've been able to get a workaround that seems to work for any StretchLegs setting I use. The key thing I've found is to simply not conform the footwear to the figure. I'm not exactly sure how you and LittleFox do it, but I just can't seem to get footwear to cooperate if it's conformed to Aiko or Hiro. So, instead, I tried a different tactic:

First, with the figure still in zero pose, I apply the character. At this point, it's easier to simply not alter the y-trasnistion setting until after the next step.

Second, load the footwear, then parent the footwear to Aiko or Hiro's body. Not the hip, as that seems to have some odd results: the body.

Third, apply your pose to the character. The footwear should follow wherever you put your character, because of the parenting.

Next, once your character is posed to your liking, apply the same pose to your footwear. This may require you to save your pose in the pose library to do so. You footwear should be posed, now, iin the same position as your character, although the fit should look pretty bad.

Finally, adjust the y-scale settings of the thighs and shins according to your StretchLegs settings: 110% = 1.00, 120% = 2.00, 130% = 3.00, and so on. The footwear should suddenly fit the character perfectly!

This works in animations, too, if you begin, in the starting pose, with the shin and thighs already scaled. Just remember that the y-scale settings may reset after you've applied the end pose to your footwear, so you'll have to adjust the y-scale settings, again, to the end frame. The footwear poses along with the legs!

Unfortunately, this method doesn't work with all footwear. The reason, from what I've seen, so far, in my experiments, is that some pieces of footwear behave oddly when posed without being conformed to the character, first, as if IK settings are turned on. However, when you try to turn it off, that option is greyed out. I don't understand this, and if someone can shed light on this bit of oddity, that'd be great! until then, I've got a workaround that will only work if you have a setup room available, or if you know how to alter bone structures in figures without need of a setup room. Basically, I just replace the bone set for the footwear with one I had prepared from the Blank Aiko .cr2 file. After that, the footwear behaves just fine. Morphs from the original footwear can be transferred to the modified footwear with this free program... what was it called? Morph Manager? I think that's the one.

I should also mention that some pieces of footwear have an odd bit of pokethrough, too, when the leg is bent at a certain angle, and I'm not exactly sure why. I'm going to try to see if I can use magnets to fix that bit of pokethrough.

And that's about it for my workaround. Like I said, it doesn't work for all footwear, but it can for some. I'm also currently working on a footwear pack that will behave properly for this particular workaround, the tutorial of which will be included in the readme. I was really hoping that WW2 was going to allow me to add that my footwear won't need this workaround because they actually have the StretchLegs morph, but that's okay. I'm just glad that I have a workaround that I can be happy with!

I dunno... would it be a good idea to package this up as a tutorial with nice visual aids?