Rubicon...sounds like you found your problem.
Don't overthink things and take the fun factor out.
The old "you need them, you don't need them" argument about PV's and RPV's is silly.
There are so many variations within these homebuilt Hot Rods that the argument is totally pointless.
Some, like me, will find the need and make good use of the parts...others will have absolutely no need for either!
You CANNOT file all these cars into the same folder and make the blanket statement that the parts are either 100% required or 100% not required.
There are soooo many small differences between similar cars that there is no simple, easy answer.
Tire diameter, tire width, rubber compound VS road surface, rotor/drum diameter, self or non-energizing brakes, coefficient of friction of pad/shoe material, pad surface area, caliper style....it just goes on and on.
Put the car together with quality parts and test.
IF you need something added its not rocket science to make the change.