I still have my Extra Special 40 which is almost identical to the Fun 51 with the exception of the shape of the profile. I am in the process of enlarging the elevator and rudder. The easiest way to add the extra length is to take a 1/2 wide balsa stick and just lay it inline with the trailing edge of the rudder and elevator and draw your new trailing edge. Doesn't get much simpler than that. I powered mine with a .46FX and the vertical was unlimited but pull was slow out of a torque roll. I have since found that the BB .46 engines like the APC 12x4 prop better than the 12.25x3.75 apc prop for hovering and throttle response. The narrower blade gives the engine much better throttle response. Also, I know the tower muffler is cheap at $12 but pales in comparsion to the rossi mini tuned pipe conversion for the .46FX sold by Morris Hobbies. You can find them online. The rossi pipe cost more but the performace difference is large. Better torque, smooth as silk midrange, and lightening like throttle response. It produces at 1500+ rpm gain using a 12x4 APC. This is like putting a afterburner on. It also fits the plane better than the tower muffler too. It does cost around $54.00 but is worth it completely.