Thank you for this thread! Actually I was searching for the exact same thing some month ago but wasn't able to find anything. So I hope some more people will join this thread.
I guess it's not easy to find pornstars who have good looking abs in general. So it would be easier to recommend single scenes.
For now I have found one amateur scene. It's not a great scene, but I think the performing girl has a really nice belly.
http://veterperementour.ru/showpost.p...postcount=2551
