For the life of me, I can't imagine a guy with one that size, I really can't (nor do I want to). I really think you did the right thing, turning him down.
But, correct me if I'm wrong, doesn't the vagina also double as the birth canal? I only mention this because, if given enough time and stretching, it could work, couldn't it? I'm not advising it, or rooting you on or anything, I'm just saying if done properly, it should work, I would think. Just wondering.
I feel sorry for the poor bastard, though. Hope he can find somebody to accommodate him. Every man's dream, but be careful what you wish for . . .