29.8 on one clamp with a nc17 post, the post is fine on 3 other 27.2 frames so its not undersized i think, and my other 3 27.2 posts (thompson, gd, on one twelfty) do the same so the frame is slightly oversized i think, 27.3 ragley is next
EDIT i'v tried pace carbon stuff and it was a bit better but i still have to crank the seatclamp silly tight to stop slippage, as in fookin effin tight, enough to make me a bit nervous about breaking something
EDIT 2 if i undo the seatclamp the post just drops to the head instantly, non of my other bikes do this if i undo the clamp on those the post slowly slides down a bit not drop like a slidehammer