I'm on a team and we are design our own aircraft. We have designed a bi-wing and we have to carry a lot of water to score high in the competition. The overall plane is going to weigh around 7.5-9 lbs. Speed is not a factor just need to fly our completed mission before we use up the allotted battery storage (1000 mAh) trying to figure out the best propeller to use for the best efficiency.