Have you considered adding what some call an A/C "idle-up" solenoid? You set your idle at 500 (475 or whatever) and then when the A/C is on the solenoid pops out and once you increase the throttle, your idle stays at whatever the solenoid is adjusted for as long as the A/C is on. When it cycles off, naturally the idle drops back to 500 or whatever. I've found setting my idle at 475 or so makes my timing work better and my idle is fine as long as I don't try to run it too rich. Because of the PCV I richen it just a wee bit but not much.
