Best suggestions so far, I think. Missionary would work as well if you keep your legs closed as that will keep the base of his penis a few inches from your vaginal opening.
Something else that has been suggested is using a donut shaped cushion around the base of the penis so that only the remaining portion can be inserted. I tried google but didn't get any product results. You may have to craft something of your own for this purpose. I would suggest a medium firmness foam wrapped with something soft, smooth and pliant. No idea how washable these would be. Also don't make it too tight as it might act like a cock ring swelling his girth.
See thread.
http://www.lpsg.org/11506-adapter-depth-control-during-sex.html
I think most of the cats are busy clawing someone elsewhere at the moment. This isn't the present forum of choice.