I think the scaling issues will always be a matter of adjusting the actual patterns. You can only scale so much before its too small for your limbs to fit through. I wish I could say there is a magic formula, but when I scale pepakura, I scale every piece individually of the others. And this isn't pepakura at all, lol. Best suggestion? Maybe cut sections out of the middle of limbs? Loss a row of plating from the chest? Ultimately anything you do will have an effect on the design, but remember, you're doing this for fun.