Residual pressure elimination

Customer car 1970 Demon street/strip.
Just installed a new manual disc brake conversion brake kit from The Right Stuff.
Front brakes and master cylinder.
Installation was smooth.
Retained rear drums
Bled system several times via gravity, back bleed, then pressure bleed.
The front calipers retain pressure, thus dragging the rotors. I crack the bleeder, a little spurt, then the rotor turns freely.
Pump the brakes a couple of times and they lock up until I open the bleeder to get that little spurt.
Calipers are plumbed direct from M/C into a T then to each wheel.
Rear drums do not lock up.
Any ideas ?
The Right Stuff is now owned by Restoration Parts Unlimited and they offer zero tech assistance on their website.