I hear you on the "pressure relief" side of things...and the problems we are all trying to overcome. What we have found is the only way to effectively control "block pressures" is to get rid of some of the volume before it goes through the motor. While I'm sure there are several ways to skin the cat, this system works on Naturally aspirated set-ups. My water temps are 150, or less all the time. We never touch the flow control once it is dialed in for maximum pressure. There is a slow stream out the dump at idle, and a little stronger dump at higher speeds (not a big increase though, just slight.)