I am going back and forth on what I should do with my new E300 DJI Hex motor kit. I have an existing 550 with the red motors. I also have a 450 with pieces parts from a Phantom I built. I have spare 450 and 550 upper and lower plates. I am trying to figure out which new build will give me better flight times. I could take the E300 motors and put them on the 550 or put them on the 450 and have 2 spare motors and esc's for the 450 and use the arms from the 550 for spares. I did some math (using a 5200 mah 3S 35C battery for both copters) and it looks like the 550 would come in around 1900g and the 450 around 1500g using the same electronics on both. Granted the 550 can lift more but it also has to power 2 more motors. I know I would probably have to have a second battery on the 550 to get close to the flight times of the 450 with a single battery. My goal is longer flight time, any advice or suggestions are welcome.