Hmm, don't know if I believe the motor specs.
300 watts divided by 18 amps is 16.666666
So to get 300 watts at 18 amp draw, it would need 16.67 volts. That's 4S power, and specs say 2 to 3S
Anyhow, I ran the motor specs on MotoCalc. 3S with a 9x6.
16.7 amps, 24.0 oz thrust, and prop speed of 47 mph, so approx 40 mph airspeed.
Approx 109.5 watts.
So at best 50 watts per pound for your set up.
Basic trainer set up at best I'd say............