bigger rear disc in rear than front a problem I assume?

Only reason four piston calipers was a thought was to account for the rear disc being larger 11.2 rotors on the explorer 8.8.

If I could keep the disc brakes that came on the car, I would, but the extra room in the engine bay the hdk gives me is worth swapping brakes, even if I need to go to 17's, but am asking these questions to see if I can keep the cop wheels