RE: Cox .049 max RPM?
I don't recall what that TD.049 tached on the ground..but that inflight rpm "song" was what I heard the very 1st time I started up a Norvel AME .061 with a 5x3 prop and tached it on the ground.
It ran at 26,500 right out of the box and it made my jaw drop.....[X(]!!
This would have been about 20 years ago..[how time flys].