I would try the 6X3 prop upgrade first before going brushless. I can speck mine out 3 times on a 600mAh 7 cell nicad pack. The great thing about this plane is that it is cheap and a 5$ prop will keep it that way. I have built 3 of them and they all require washout on the wings to keep from severe tipstalling. CG should be moved back 1/8-3/8" for good flying also.