Rear disk conversion issue

Update. My brakes are satisfactory and stop the truck but, I don’t like the pedal travel. I had one front caliper that was sticking and little to no grease. When I have either front or back connected, then pedal is extremely hard like it was with manual brakes. When I hook up both front and back, the pedal moves 2-3 inches. I know it moves some with PB but not that much. It sure seems like a fluid volume issue. I was looking at a 1 1/4 MC. I’ve also considered a 2 psi RPV for the rear disk even though I shouldn’t need one. Thanks Craig