If he is seven inches and you went to a place where most men were longer - you stumbled on a bit of a freak show...
Then again, he could have the same problem a friend of mine has. I have a buddy who always looks around at guys who are naked at the club and wildly over guesses their size. "Gee, he's eight inches if he's anything at all" or "that horse is definitely swinging ten."
I like having him around because I know he is similarly over guessing me as well
Truth is - he does that because he has himself stuck on six... Well - he's actually lucky if he is just over five, but I think it makes him feel good to be "average" and then just assume everyone else in the world is well endowed.
Guys who are fixated on penis size are very unlikely to be very good swingers. Your husband needs to overcome this for himself - but until he does - he isn't likely to enjoy himself.
Spoomonkey