Yep, thats it Steve. A mate rides the e160rs and that has the intergrip one which is like a bolt through the frame which has a slight cutout for an interference fit with the seatpost. The interference bit has a taper at each end from memory. TBH it seems like a needlessly over engineered...
A bit late perhaps but if it's 6nm then my guess is that it is an intergrip clamp, not the standard sort. Might be too late if you already crushed it but I would have suggested taking the intergrip bolt out and stripping it right down and greasing up the tapers to make sure it moves smoothly...