Not sure why you may have experienced problems with RFI, Vanguard. I have had success with both C&H and DA ignitions with no issue. All of my receivers for my gas planes are Futaba PCM, DP149's.

Some other tips for the RCATS:

END POINTS
On the RCATS switch, both end point settings are important. Otherwise, the contacts will chatter. You will see the LED light blipping on and off when this happens. On my Futaba 9C, I make the endpoint only 10 points or so higher than it takes to engage the switch. I do this in both directions. If it requires an endpoint of 30, let's say, to just barely close the switch (green LED turns ON), then I will set that end point to 40. Some folks automatically set them to +/- 100 for a switch. That's a bad idea in this case...the RCATS switch will not be happy.

LOCATION
Since the RCATS switch is switching over the ignition battery, at least one end of the switch potentially has RFI passing thru it. I locate my switch fairly far forward in the plane, not close to the receiver. It's probably closer to the ignition module than to the receiver.

I hope this helps.