Does anyone out there know how many pounds of thrust a Kress RK-720 (3 and a half inch diameter) fan puts out??? I also need to know what the maximum RPM is that I can put into the fan before it stops pulling and starts chopping air. I am looking for the correct motor (.25 size) for the most thrust and was contemplating the Dubb Jett .35 (built on a .25 case). I am afraid the Dubb Jett motor will have too much power for the fan, or that the fan is too small for that much power and over-rev the motor. Any insight from the model engineers out there will be greatly appreciated.