How much setback in seatpost when using the rear facing (road) clamp position?
The exact seat tube angle would depend on your seat height and position of the saddle. I believe generally, it’s around 73-74 degrees. (the Cervelo website has the exact numbers per frame size)
There is also a calculator of sorts in the tech section of the main Slowtwitch site that uses the seat height etc… to give you a more precice measurement. I’d try that.
Excluding saddle height and angle, does the clamp not have an inherent amount of setback, i.e., 1.5cm or 2.5cm, etc.?