I learned something very important today about this from an experienced 3-d flyer...He came up with this equation 10 grams of battery weight = 40 watts of power. I was assuming that my 2100 mah batterys would b more than enough for a plane that recomended an 1800 mah battery( omega 72 setup). i flew my plan and it was somewhat underpowerd. So, I started asking a bunch of questions (almost in a panic because I thought my plane was stuck this way). But my 2100 mah battery was only producing about 300 watts of power while a heavier 1800 mah battery will give closer to the recomended 500 watts for my plane. I also assumed that a 4 cell would be stronger. But, my new best friend explained that cells= volts and volts are used to adjust prop size. i wish there were a place that gave and explained these formulas....