I use the PBSF on my backpack, which has a pocket area that it clips onto. I am thinking about buying the rack adapter to put it on the back of the rack. There is not room on my seat post because of the reflector that came installed on the bike.
I also have two cateye ld610's that I put on my panniers (axiom lasalle with straps for lights) or on each seat stay if I ride without the panniers.
I also have fenders with reflective tape going down the rear fender.
I have the PBSF set to blink and the ld610's on solid.