Biopace? From what I understand -- and jump right in and correct me if I'm wrong -- those work fine on multi-geared bicycles because the derailers pick up slack in the chain. But on a SS setup, the chain tension will be changing pretty dramatically as you crank an elliptical ring. Have you tried just spinning the cranks and checking how much the chain tension changes in the course of one revolution?

My suggestion would be to put a round ring on there and see what happens.