TMI brother.Hough: do not ask an ER doctor how fat people have sex.
That being said, I have two stories. One lady had a horizontal bruise across her lower abdomen. When I asked about this she laughed and said don't worry about it, I use a broom handle to hold my fat out of the way when she makes love.
The other one is more difficult to visualize. It involved opening up a kitchen table so that there is a gap where the next leaf would go. And then standing in that Gap to hold things out of the way. I'm not sure how the second person comes into play.
Also heard of a neighbor that would come over and hold things back to allow it to work.