i agree with you, Removing those valves would lock up the rears in ANY heavy breaking situation. The rear pads are smaller and would wear too fast and overheat sooner too.
What we've done on the IT scca racecar is to place two manually adjustable proporting valves next to the Drivers seat to adjust the brake bias. Two valves to maintain the safety / split circuit system. it's not hard to do you just have to route new brake lines into the cockpit. They could be mounted under the hood, but they are touchy to adjust and i think would be less safe on varing road conditions lan the simple limiter that was stock. BTW i've "raced" a stock 142E for a couple seasons until I got fast enough to need a race seat and 5 point harness to keep myself in position.... The stock brakes with good pads were Never a problem
Unless you are trying to coax the last few millisenconds out of a lap at the track I doubt you'll notice the difference. Generally we only adjust the bias for Rain when we are trying to stop and not loose control at the edge of traction wherever we can find it.
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71 142E , 71 142E ITB Race Car, 90 240 250K miles, 92 240 family car (very sticky back seat-yuk)