As I'd mentioned earlier in the thread, I use my military ICW sleeping bag in my hammock.
I have been sleeping inside the bag, and it works fine for me as long as I've got a pad under it or the hammock.
The comment about gear being made for munchkins is one of those things that I've been concerned about. I want to go to a lighter bag, and prefer mummy bags...but don't know if I'd fit decent in the ones I've looked at.
I'm not huge...5'6" and about 200lbs. But I'm used to have plenty of room inside the bag, and don't want to lose insulation because the bag is compressed over my shoulders/etc...
I'm going to do a test run with my adult son's 0* mummy bag sometime soon, just to see how it works out and make sure it doesn't compress too much around me.