You could get a used Rossi65,81,OS77,91 or K&B 82 with A Dynamax fan and just run the engine rich and it will last longer and they are just as cheap in the long run and you can get the parts all over the place.The little engines are fine don't get me wrong but the biger ones with the Dynamax will help you get off the ground faster and they are the same size as the Turbax fan.You will only gain A pound in weight and the thrust will go from 6 or 7 lb's to ten lb's.It's goin to be your decision on what you would like.A turbax 111 fan is the same as the 45 fan with a biger motor mount,to me it does not make very much sense.I know of people that has A Turbax111 fan that put a turned down Dynamax rotor in it with a old OS 65 and they last A lot longer becouse of the rpm's.Somthing to think about.Take care-Mac