Based on how a lot of Superheros are drawn especially in the TV Cartoons, they always seem to make the upper torso much bigger than the legs anyway. I wouldn't worry about it for a second. Besides, you can always modify legs of future customs if this doesn't end up working for you. I think it is a great looking set up. Fred does nice work, I definately need to pick up some of these. Please share photos when you are done.
"Steel-like jaws clacked away, each bite slashing flesh from my body - I used my knife and my hands, and when they were gone, my bloody stumps - and yet the turtles came."