Ok to use 7x9 carbon saddle rail in 7x10 clamp?

[Mep]

I was in the exact situation and ended up with using my Berk Lupina with the 7x10 clamp. If you measure your saddle rails, do they come up to over 9mm? That was the case with mine, which led me to buying the 7x10 clamp. It has worked well with no slippage.

That said, I'm surprised the 7x9 clamp mates well with the new Madone seatpost. Visually it looks very different, the 7x9 is triangular not round and doesn't have the sleeve that tucks into the seatpost. The guidance I've seen online is mixed as well, Evan Cycles says it's not compatible with the 9.9 but the 9.2? Pretty confusing.

Trek is very a much a nickel and dime company. I bought a $4000 frame that didn't come with a seatpost. I bought the $275 seatpost but it didn't come with a clamp that allows use of carbon rail saddles. You would think most people building a $10-12K bikes would most likely use carbon rail saddles, right? And now this. Here's a pic of my Bontrager XXX 7x10 saddle which is currently on my TCR next to the 7x9 Berk Lupina.

That's bizarre, I was pretty sure Trek included the seatpost with the frameset albeit only with the clamp for round rails. Has that changed with the SLR?

Those rails indeed look different. Sounds like FIJIGabe doesn't need his 7x9 clamp though, maybe worth a try for not much cost? If you do take that up, let us know how it turns out!