I have the sides pretty well set with the Spanish Cedar support wood in place for the arm bevel and the cut-away bevel. I'm careful to hollow these supports out some to save weight and air volume. This theoretically also helps with bass response. Of course, I have no way to test that so like many things on a guitar I'll put it in the best practices category. In any case, it saves weight and body air volume which is what I want and even though it's on the inside I think it looks cool.
I do have to say that if as builders we only did things that could be absolutely proven, guitars would sound like crap and would stay that way!
Anyway, here's a picture:
M