As John knows, I'm with him. I replaced my prop valve with otherwise stock brakes. My rears don't lock and the pedal feel is not to be believed! I autocross the car and don't have any of the problems that are supposedly a consequence of having done the replacement The part cost $12.00 at a local VW shop and took about 1/2 hour to replace.
Here's a thought. If you don't mind blowing a couple of bucks and like to learn something for the investment of some time, try the swap! Of course you do have to do a very thorough system bleeding. If you don't like the results, you can always go back. I'd be willing to put some money down that you would never replace that prop valve.
Good luck!
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Herb
'72 1.7 Tangerine 'Teen
'74 2.0 Red Rustmobile