One of the advantages of being overweight for me is that when I don't bind, people just seem to assume that they're larger than average man-boobs, because I've gotten sir several times when not binding. Although, for my size, they're not that big. I wear something like a 44A, which I don't even think they make, the smallest cup size I've seen with that size is a 44C. But I haven't worn a regular bra in years and years, only sports bras, I don't have to worry about cup size with those.
I do wear a binder sometimes. I wore one today for several hours while I was out doing errands and when I got home, my chest was hurting so bad (I don't bind that tight either). Couldn't breathe, even still had trouble after using my nebulizer. Ugh. I think I'm going to have to give my chest a break tomorrow. A few weeks ago, I actually woke up one morning coughing up some blood after binding for several hours the night before. So I do have to be careful.