I was recently thinking the same thing about a cup seal. It seems to me that if it was shaped like a football (maybe with a similar valve face) that you might get better flow through it. Also, AKA came up with a pretty unique design with the flower shape (for lack of a better term) that might have some potential. They might have a patent on it though.
I think you might get mixed input on this though. I find that folks who have figured things out or have some financial stake in products tend to keep their own findings to themselves.