I have ridden several different clip pedals over the years and your point about lots of float holds true for me as well. I end up riding a bit duck footed with my left/rear foot that wants to further rearward to compensate for the uneven feeling. Well broken in crank bros systems work for me.
My body is pretty uneven as well from a variety of things as well. Counter point though, I like the grip and muting of Impact Pros for trail riding on full suspension and hardtail. Smooth easier trails, I prefer a softer sole with a little less grip that makes it easier to pop and play.
I would be interested to read an article on uneven foot placement from your perspective. Keep up the great work! I like reading the kid articles as well. I appreciate the elbow pads for knee pads idea and all the other ideas for making it more fun for my kid!