My first plane is a GWS Slow Stick. Currently with a new Ni-MH 9.6V 1100 mAH battery installed the plane won't rise more than about 2 feet off the ground. The plane weighs 24 oz ready to fly. The assembly instructions say the flying weight should be 15.9 to 21.2 oz. Would the extra 2.8 oz keep the plane on the ground? If so would a more aggressive prop overcome the weight problem? The supplied prop is a 10X6 I'm thinking of going to a 10x7 or 10x8. Any advise would be appreciated.