where is the proof that a shimmed seatpost will screw up your frame?
Yes - get the right thing the first time, but if deathhare wants to keep the seatpost, a shim might work. I have seen a good number of bikes with seatpost shims (the USE Alien suspension posts required one for certainm size frames) without any ill effects.
http://images.google.com/images?svnu...=seatpost+shim
the hard part on this request is finding a 26.8 to 27.2 shim...
biketoolsetc and loosescrews have nothing in that range and it appears to be fairly uncommon.