Dave, you are so right! I learned alot from Model Airplane News 'Ultimate Electrics' publications. A great formula: sailplanes, etc 75 watts per pound, sport - 100 watts per pound, 3d - 150 watts per pound. Watts = battery voltage times motor amperage (i.e. 60 amp for this motor). Two 4s lipos in series gives me 8 cells or about 30v x 60 amps or 1800 watts. Can easily lift 18 pounds which is in line for a telemaster and guy with room to spare. 5000 mah gives us 5-6 flights with a reserve charge.