I have just snapped the rails on a Phenom Pro after 5 km of use. It's on my 'cross bike at the moment, but I was planning to use it on my MTB. I wanted to try a dis/re-mount to see what the saddle would feel like for cross. On the packaging it says that it should be fine for 'cross.
I sent an e-mail to the Specialized Concept Store where I bought it (with pictures attached), and now they tell me that it snapped because I used the wrong clamp.
The seatpost is a Thomson Masterpiece. According to Thomson (http://bikethomson.com/seatposts/masterpiece/#FAQ
Q – What size saddle rails work with Masterpiece seatposts?
A – Saddle rails from 7 x 7mm up to 7 x 10mm work well with Thomson Masterpiece clamps.
Q – Will carbon saddle rails work with a Masterpiece seatpost?
A – Yes, our clamps are very gentle to carbon saddle rails.
The rails of the Phenom Pro are 7 x 9 mm, so I really don't see the problem here. Anyone else with similar issues? Is the Masterpiece not fit for the Phenom Pro?