Let me try to simplify, and add a little something to this discussion. First, if the caliper piston is rotated back into, and fully seated in its bore, there is literally GOBS of room to slip your pads in. Even more than the fronts from my experience. Just PUSH in on the piston while turning.....with your needle nose pliers OR the handy-dandy little special tool.
As for the rotors, unless you have a tool with dial gauge to check your "runout", you should leave the rotor in the same position. Rotor position on the studs should be changed for really only ONE reason...... If you DO check the runout, and find it marginal or OVER specifications, OFTEN times that can be corrected or at least made BETTER by re-positioning the rotor on the hub. Feel free to e-mail or call me if anyone would like further or more detailed information.
King
GreatBrakes.com
(866)GR8-PADS (Toll Free)