are these aluminum rear calipers junk or is it me? today i installed new, pads, rotors, reman calipers. and bled the rears. the old pads were worn inconsistently. inboard pads were shot. outboards were hardly worn. about 14K miles since last replacement. is there to much flex in the calipers? or is it because they are single piston calipers? is it possible to upgrade to 1500HD dual piston bakes? is a cast iron single piston caliper available? also the brake pedal still seems mushy. when i bled the brakes i used a QT of dot 3 brake fluid thru the rears. i bought this truck used in 2007 from a dealer and they had installed new brakes then. i seem to remember the pedal being firmer then. did i miss something while working on it? im 48 yo and have been doing my own brakes, tune ups, water pumps, alternators, tstats and so on since i was 15 yo. basic stuff i can handle. any thoughts, suggestions or advice would be appreciated. thanks in advance, dave.