So I put on a used (new to me) aliante on last night and noticed that the shape of the rails didn't match up with the shape of my seat post rail clamp (race face post).

It seems like the post clamp has a slightly different diameter than the rails. So instead of clamping all the way around the rail, it's only touching at 2 or 3 points. I think an easy (and extremely exaggerated) way to imagine what is happening is if you clamped a circle in a triangle shape.

Has anyone noticed a similar thing? Do different seat post rail clamps have different sizes?