I had been planning to use my Eagletree with an optical rpm sensor, but after several inverted poweroff landings with that darn Fox, the data recorder kept getting ripped off the fuse-bending the pins. I had velcroed it to the Skyray canopy area for convenience, since I had forgotten about those good old days of getting a side mounted Fox to behave.
So I backed off using it, and since the sound is working so well---and giving an additional bonus of seeing when the engine goes from 4 stroking to 2 stroking (for those engines setup that way), I haven't put the data recorder back on.
I am planning to post some data I took yesterday with my Nobler with a Brodak 40. This was the Nobler Arf I was flying before I converted another one to electric.
Anyway electric is a lot easier to understand what is going on!