The Stabilizer is a great reg. I've been using mine for 12 years now without a hiccup!
I have run HPA most of the life of the reg, co2 only rarely.
The rule of thumb for multiple regs is to set them 200-300psi apart. It's about the "recharge" time of each reg. It comes down to restricted airflow - if you set Reg A at 350psi and Reg B at 300psi, Reg B doesn't have enough 'backpressure' to fully recharge [i.e. give desired output pressure] when under heavy fire.
The output of most HPA systems is right around 850psi (the typical desired CO2 tank output so CO2 markers can use them).
Set your regs accordingly.
My Stabilizer is set to 310psi
I get +/- 5 fps