Most of the time, not always, but most- guys will be sizeably larger then their girls. So wearing their oversized stuff kind of evokes a protective feeling of sorts. At least that's kind of how I feel. Primal's like 3X's my size so his shirts come to my knees, which is cute. However having said that, I think you can gather why him wearing ANYTHING of mine would result in total destruction. "Hulking" out would be right. I do think it would be hilarious, but not sexy.
Along the same lines, I've tried for years to get him to dress as a woman for Halloween. Of course he couldn't wear MY stuff for that! He wears a men's size 16 shoe though, and I have no idea where I could get women's shoes that large... I've really given this a lot of thought.
/plotting