yea, that is a limitation of SL, because as an avatar it can only be worn on human body, and clearly battroid's shape doen't fit so well. That's why adjusting joint is so painful, and indirectly it affects battroid's body shape badly.
Another bad thing is that SL accepts only NURBS mesh within 16x16, so there's no mesh smooth for that. It's much painful “sculpting" in this way, since you can't add or remove any point or face, because the geomerty UV must be clean