Roger, I would almost agree with you but I put the kit on from MPB and it could not have been any easier, I have zero issues, now keep in mind 80% of braking is done by the front and my rears could be siezed tighter than a drum and I might not know it yet!
As for Navy, I still say either incorrect volume (too big) on rears or sprag is siezed.
1.) Volume issue, you could not probably physically see the size difference, heck a Wilwood is twice the physical size of a GM and holds way less volume even with 4 pistons so, you could take one of the front calipers off swap it with the one of the rear still, don't hook up of e brake and hit the peddle if this is the case, on the front brakes the smaller volume caliper would collapse and the other larger on the front would not, problem either solved or eliminated about 15 minutes on a bare frame as the caliper mounts are the same for these. if they both stop the rotors while pressure is applied when you are swapping them back simply crank the e-brake arm and see if they are ractheting.
I know this to Navy is about 6 guys barking commands from their easy chairs but this can be figured out and eliminated pretty easy, if both collapse at the same time when you have a rear and a front caliper on the front and then find they are ratcheting I would then start eliminating valves etc. But swapping calipers is free (no fittings to buy) and would also confirm or check the valves to some extent since both calipers could be compared on one end of the vehicle with the same valving.