This is True.

In my R30 I had a Webra-35 which refused to run correctly. Lots of flameouts, and would bog down while hovering. I assumed that it was running lean, and kept richening...

Finally got a non-contact thermometer - a cheapo one from Radio Shack. Did a bit of research, and found that most .30-class engines are happiest with a running temp around 220-230 degrees.

Fired up, hovered, then tested my Webra... 192 degrees.

Leaned the engine to a consistent 220 degrees, and damn if it didn't run perfectly.

I have a R50 now. Its a ringed engine and is still breaking in, so I'm running it a hair on the rich side at 210 degrees. So far, so good.