if you don't extend past the 'max' mark on the seatpost and the seatpost extends about an inch or more past the bottom of the toptube, you should be fine.
Ideally, there should be an equal length of post extending below the centreline of the toptube as there is from the T-T centreline to the top of the seatcluster/ seatclamp.
Last edited by caterham; 03-12-08 at 12:21 PM.