Bought a p9 frame myself, delivered a few weeks ago. Seems to have plenty of rear tyre clearance, even with 29er wheels. As for 160mm brakes, I've seen plenty of builds with 180r/203f combo.
As for geometry, I'm looking to put a 170mm fork with-1 degree bushings on the shock, should slacken the head angle to somewhere between 64-65 while keeping the seat angle reasonable.