Not necessarily. It seriously varies in my experience, and I've been with both body types. Most guys of any body type will be about average. Some bigger guys may have some fat padding their pubic bone that makes their penis LOOK smaller than it is, but you can tell their true size when you actually get physical with them, because that fat is soft, it 'squishes down', for lack of better terms, haha. I actually kind of like that better, in that us both having a little bit of fat there, slamming pubic bones together when things get rough isn't painful.
It might be optical. A 7" penis looks differently on a sumowrestler than on a skinny midget.
Generally, body height has the best correlation with penis size. That does not mean that every tall guy has a big one and every short guy has small one but, on average penises get bigger if guys are bigger.
from what I heard it's because some how the penis can't stick out as far because something to do with the fat. I'm not sure how it works but it might depend on where the guy is fat and lot's of other things.
using it as a kick stand isn't a good idea. someone might kick it out from underneath you and make you fall on your face.