About 5 or 6 years ago we got talking to another couple in a swinger club bar. They were mid 30s, younger than us; the woman was VERY large and I didn't fancy her much while her guy was normal size. I could tell my wife wanted the guy so when she suggested a 4some I went along with it. We found a private playroom with two single beds and my wife and the guy got down to it on one while I was left with the enormous woman. When we came to fuck, I found it difficult to get my cock into her mish style, so turned her over into kneeling doggy. I had difficulty there, so leant her against the bed while I stood behind her in standing doggy and managed to get in. I kept on slipping out, she was so fat, and was really in danger of losing my erection, but eventually managed to stay in her cunt and started humping. She seemed to be enjoying it from her noises, but I just knew I'd have difficulty cumming - I wasn't enjoying the fuck at all. After a while she reached around and started fondling my balls, which was nice, but soon after she squeezed them hard, agony! I pulled out and lost my erection while she apologised. I suggested we left the other two to it, and went to the bar; she seemed OK with that.
My wife and her man appeared later, they'd had a really great fuck so someone was happy! We found another couple later with a normal-sized woman who was a really nice person and a great fuck too, so the night wasn't wasted.