P3 Rear Brake - Adjustment Question

Put in my first few hundred miles on my new P3 this past week and I noticed that the rear brake is very, very wobbly and I don’t think it was set-up quite ride…

B/c of the cut-out, I can see that you don’t tighten it the same as a regular double-diamond frame - so how do I adjust/tighten the rear brake so it won’t be so loose…

If there are any wrenches out there with P3 expertise - I’d appreciate any feedback…thanks!

Cervelos web site has a technical page that discusses the brakes on a p3.