Just a little entertainment this morning.

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I'm not saying that the rear adj proportioning valve is a bad idea.......You may be able to balance it just fine. I don't know.

If yours is a foot braking car(assuming it a auto car) it might hold a little bit more stall pressure, without pushing it thru the lights.
mine is a factory drum brake car with the factory drum brake proportioning valve that i put disc brakes up front with a new disc brake master cyl. so it's a bit of a mismatch. but i can't hold my car under full throttle. pushes thru the lights.

Adj the proportioning valve to 0 resistance may make the rear brake lock up first and and im just taking out my arrsss(and i am)
It would be interesting to know how it all shakes down with a panic stop.....before you have to do a panic stop.