drum brake proportioning valve

I bought the master cylinder that was recommended for my car from folks here on the site. I am not putting Disc on the front. What I read it seems as if drum/drum systems need residual pressure valves to keep back pressure on all four drums? Any one know more about this? Here is some info:

Residual pressure valves are required for the proper performance of your braking system. There are
two different residual pressure valves with different ratings:
10 lb: A ten pound residual pressure valve is needed to the drum brake portion of your brakes to maintain
a firm pedal. The springs in the drum system will pull the drum brake shoes back in away from the
drums. The residual pressure valve maintains a pressure in the system to counteract the spring tension.
This allows instant activation of the drums giving a firmer pedal.

HOW DOES THE VALVE WORK
The residual pressure valve has a one way “duck bill” valve inside which allows fluid to pass in one
direction freely while restricting the flow in the other direction. The spring inside will hold a residual
pressure to a certain point and then release above that maintaining the calculated residual pressure.
To install the residual valve into the line, cut the line and re flare both ends
with a double flare. Install and tighten.
Fluid freely passes this way
Master side Brake side The one way valve prevents fluid from passing back until the
spring tension is overcome and reverse flow can occur.
Depending on the spring rating this will be either 2 lbs or 10 lbs
pressure. The valve will then close once this level is reached
keeping the residual pressure on the other side.