a speed 400 parkflyer should weigh no more than around 24oz ready to fly. my rule of thumb is: .049 sportplane=speed 400 direct drive, 049 biplane= speed 400 geard 3-1, 049 cub type of plane= tall geared speed 280 (electrofly 5-1) or for a lot of power also more weight a geared speed 400. I bought a old Sterling tigermoth bipe that has a 32 or so span and fly it on a geared 280 with a 8 cell nmih 720 and fly for 30 mins. just love it. hope this helps, Mike