It's certainly possible that Japanese might have more curve progression because they half smaller frames on average than Europeans. I'm not saying I know anything about that but it's possible.

Everything I read suggests that in general the more muscle the better.

Oddly enough even before my son was diagnosed and I knew anything about Scoliosis I had a sense that it was a small person's disorder. I know that's a stereotype but you don't automatically think of The Terminator and Scoliosis together.