Joined: Jul 2007
Posts: 64
Likes: 0
From: Minneapolis, Minnesota, USA
Bikes: Schwinn World, MOAB, Varsity; Trek 820, Miyata Five-Twelve rebuild
Check to see if it is just your 27.0 seatpost or all 27.0 seatposts.
The best solution might be to have your LBS use a seat tube reamer to evenly shave off a bit of the inside of your seat tube. I have done it before to my frames with great results.