I think it's going to be trial and error. With so many cruisers configured so many ways it will be impossible to determine what brake options will work for you. If we could have a post where everyone describes there non stock brake setup and cruiser configuration then we might have a chance of helping someone. Though the proportioning valve gives you a better range of adjustment it may not be the best fix.
Just think of the varables.
SOA Vs. SUA (the center of gravity is changed as well as geometry
Engine (2F, sbc, diesel, etc)
Tires (M/T, swampers, A/T, narrow, fat hard soft compounds)
Brake pads used (carbon, semi metalic)
Brake lines (my rear brake lines all of them are braided hoses)
Brake boosters
Shocks ( different shock affect braking performance in different ways)
other accesories that add weight to the front or rear (gas tank location, winch, compressors, Bumpers, Roll cages, etc...)
Shackles (I'm sure my hyper shackles effect my braking performance)
Springs (some are a lot stiffer than others)
Then there are calipers (stock, monte carlo, 4runner, etc...)
And the most important Brake master (stock, 80 series, corvette, asin, etc...)
I really think it is impossible to tell someone exactly what will work for them. Considering the thousands of different configurations. But I can say that if you are not lucky on the initial setup that a propotioning valve will get you closer to your goal. I have been lucky and not had to go this route.