Interesting thing about Biopace, it's the other way round from most rings. IIRC Shimano had some reason about the momentum of the rider's knees or something. Somebody did a study I read, that non round rings could be worth a few percent, oriented the way you'd think they should be, with the tallest teeth engaging when the cranks are horizontal-ish, but with no real gain when the out of round is below 9% or something.