It's a lot more complex to regulate boost that way, not sure you can use only a ref dc curve alone - PID most likely. I haven't had luck either which is why I suggested hooking it up differently. I would use the single solenoid to apply boost to the top port, and maybe add a second valve to the bottom port just to get quicker spool (bleeding of all boost until a set pressure, not effective on many setups especially with a strong/correct spring pressure).