I HATE carbon seatposts for this reason. Carbon is really ill equipped for this role. Tacx undoubtedly works, but why bother with it? There is no functional advantage to a carbon post (because, to be strong enough, it is built to be as heavy as an aluminum post).

My new frameset came with a carbon seatpost. After 25 miles, it started slipping (as I knew it would). I'm changing it out for a Thomson. I will save 40g and I will have a seatpost that I never ever have to think about.