Just bought a Cervelo Soloist and the seat keeps moving side to side over the course of my rides. I've tried tightening the bolt down pretty snugly, but it still moves.

It appears the head tube is held into the aero seat tube by a single bolt that presses against the head tube. Is that really the proper design or was it assembled incorrectly? It seems like a better method would be to use that bolt that pushes something with more surface area against the seat post.

The way it is now, the point where the bolt contacts the head tube has gotten pretty chewed up.