I've come across seat tubes that were pinched oval from someone using too small a seatpost in them. This is how I fixed it. take a 1 1/8" quill stemand put it in with the wedge in the collar against the narrow parts of the oval, tighten the quill stem slowly so that the wedge pushes the wall of the tube out. do it a little at a time until it's close to round. Push it out so it's a little larger than the correct size seatpost. The correct size post will slide in easily. tighten the pinch bolt, and it will conform to the seatpost, pushing everything back to perfect roundness. It worked for me on a bike with a 27.2 post that had been running 26.8 with a shim. Beleive me the correct size poes works way better than a shimmed post.