Hy Mearl, the primary system [closest to the fire wall] should be plumbed to the front brakes. As you are using a master cylinder designed for a vehicle with disc brakes all around, I would suggest a 10 p.s.i. residual pressure valve be installed in the rear brake system, as a minimum addition to what you have already done. I highly recommend a combination valve for a disc drum system be installed, this would give you the metering function your adjustable proportioning valve is now doing, and if you hooked up the warning light circuit, it would provide you with a visual signal of system problems. Hope that helps.
