Im assuming your using a futaba system? (Radio\RX)
I've successfully ran this on 7 channels, there is a trick to it. You can use a Y-Harness and link it into the RPM Select menu (Say Multigov, or Rev-Max), the AutoBooster turns off and on with +/-100% pulse widths from the TX. On your RPM adjustment switch (need a seperate one instead of linked to a flight condition) and turn it off and on via that switch. You can also reverse the channel if you want the unit on at a certain switch position (I have mine down to come on). Reversing the channel will not effect the governor speed (unless you are running a Vbar governor).
You can also Y-harness with the throttle channel, but you may need a Y-Harness with a servo reverse to allow the autobooster to come on at low throttle, and off at high throttle. Or you can flip the servo arm over.
Mikado "V Team"