I'd recommend trying a different prop diameter. The speed of an 13x"11" pitch prop is to fast (70 to 75 MPH) for precision flying.

13 x 11 = 24,000 prop load

16 x 6 = 24,500 prop load


OS 90 FS max torque = 7,200 rpm

Thunder Tiger 91 FS max torque = 6,900 rpm

Super Tigre G90 max torque = 5,900 rpm

OS 140 RX max torque = 8,700 rpm


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Schpankme