Clamping down- bad mix of post and saddle?

[Robbos]

I've just installed this Specialized Power Expert with ti rails on my vintage USE seatpost. Anyone think there's an issue with clamping forces on hollow ti rails? Bonus points for those with actual experience with this set-up/issue
Thanks!
PS- Specialized says I should size down to the 143, but this 155 feels mighty comfy, cannot wait until it's warmer for me to test it out!