If you use a tuned pipe... be carefull!!! Tuned pipes are a little finicky.... You want to tune for midrange, not high end.... you also want the engine to be very reliable...... It's not pretty when your engine flames out while hovering 5 ft. off the deck... ask me how I know....

I'd go with the standard exhaust and a 10 x 5 prop and see how she goes.... Just build it really light and do the super wasp mods... You can also build up the ailerons and elevator, make the rudder out of 1/4" sq and use 1/4 balsa for the spars to kill some weight.... Don is experimenting with a built up fuse to reduce weight... My next wasp will be built this way.... He did his 1 1/2" wide so that he could mount a servo in the bottom of the fuse.... Kinda cool....