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Have picked up a lovely saddle for my road bike, but now need a compatible post. Toying with a Thompson masterpiece
Zipp service course sl...
Zipp looks nice but can't find any reference to it being carbon rail compatible
Any seatpost that clamps the top and bottom of the rails is carbon compatible. I've got a zipp service course sl on my road bike with a carbon railed saddle and it works fine.
There aren't really any seatposts that are bad for carbon railed seatposts any more. Even the posts which look like they put the rails in undesirable 4 point bending have nicely smoothed edges and wider contact points to reduce pressure compared to models from a while back. I wouldn't be fooled in thinking you need something special just because you have carbon rails.
Main thing to avoid is a post with a sharp edge in contact with the rails but these don't really exist any more. I am very happy with this [url= http://www.ebay.com/itm/Climax-Full-3K-Carbon-SB-0-Ti-Bolts-Road-MTB-Seatpost-Seat-Post-0-Deg-Black-31-6-/360869681501 ]135g £60 seatpost[/url] with my Tune Speedneedle.
I have had a Thomson Masterpiece in the past but dented it quite quickly and it is both heavier and more expensive than the example in the link. Up to you, but personally I wouldn't be paranoid about a "safe for carbon rails" section in the description. Just torque the post up correctly and you are good to go.