The double pump of the brake pedal is common on these old school brake systems, especially when the reservoir is on the same elevation as the wheel cylinders. The issue stems from the fluid draining back into the master cylinder between brake applications. There is a fix for this, and will be purchasing the fittings and documenting the results. The residual pressure valve retains 10 PSI of brake fluid within the wheel cylinder/line to #1 keep the wheel cylinder piston boots expanded to prevent leakage, and #2 to retain fluid within the line for more positive braking when the pedal is applied once. The 10 PSI is for drum brakes, while disk brakes require only 2 PSI fittings. The disks are much more efficient, so less pressure is required to keep primed, (so to speak).

I moved the Heep around this weekend, and it appeared to be braking alright, but the test will be going down the road and testing again. A stuck wheel cylinder piston would be the most logical diagnosis for this issue, and the fix would be to dump the Crown wheel cylinders and scrounge around to find some Wagner USA made cylinders, but everyone is out of stock on them currently.