I had a similar problem on my 09 Madone 4.7 (though not as bad as that one). The Madone has lots of paint on it. I replaced the bolt with one that was 5mm longer. Once the threads caught, the clamp closed up fine (still about 1/4" gap between the halves -- but flush fit all the way around).
I put the another 34.9mm Ultegra 6700 FD on another bike that I built (unpainted carbon frame) and was able to use the original bolt, but it still couldn't be turned in very far. IMO, the clamp hole is a touch undersized but paint on the seat tube makes the tube itself a touch larger than 34.9.
Bob