Still have ridiculously small rib cage

[BWalter]

I posted a while ago on this subject, but thought I should bring it up again with more specifics and see if I can figure out the exact problem.

At 17, my rib cage (and therefore upper body) is about 11 inches across, and less than 5 inches deep. I have been working out to gain muscle mass, but I can't imagine how much muscle it would take to offset this. A doctor recently told me that at 17, my spine is done growing ... does this mean my rib cage won't grow either?? I mean, I have seen other ~17 guys that are skinny (ribs all showing) that are twice my size! I have yet to see any other guy my age with such a small rib cage.

Anything I could/should be doing about this?

[Magus]

Almost nothing I presume, the bones shapes it' self. I have quite the opposite problem.
I have a huge rib cage that protrudes outwards, also which obviously stands out more than anything on my whole body. It gives me this un-proportionality through out my body.