Thinner people are better frames for building creatures on.
If someone is big they make the costume look bulky. Like Ben Affleck as Batman. He is already a big guy. So adding on top of that frame he looks stiff and bulky.
Actors like the guy who played Robocop, Predator, or Abe Sapien are all medium, to thin.
So take advantage of your size.
Your sculpting is looking good. Make sure that the joints aren't thick since you really cant gain muscle in those areas.
It will also help with movement having the joins smaller. That way there wont be a lot of thick material bunching up.