The shape of your head or whatever scars or anything you may have is what is going to determine if you look good or not. Weight/size has nothing to do with it. That's only if you want to look like a real badass.
I am 155lbs and 5'8" and I have been shaving my head since i was in my mid twenties. I started off with a real short buzz and just recently started shaving it clean. I let it grow all week, usually shaving on the weekend in the shower. If you are that worried about your physical size, then start lifting some weights and bulk up a little bit. Oh, and I'm 30 btw.