I wrote quickly and I must have been unclear: If you stand to the side of the bike and look at the drivetrain, the chain sort of moves in a triangle. Not true, I know, but the principle is the same that each leg of the chain has to lengthen as the wide part of the elliptical ring is vertical.

Check out the pics of BioPace fg bikes that Sheldon used on his website. In every case, it was a small ring. I would guess below thirty teeth. Notice also that the squish of the ellipse gets much more pronounced in the larger rings. I think that the way he happened to set up his BP bikes made it not be an issue. All I am saying is that his conclusion might not cover the larger rings.

jim