FWIW....I just flew one (H9 33% Extra) today with the servos in the stock locations (4 in the tail) and a ZDZ 80 with an in-cowl pitts muffler up front.....not at all tail heavy...in fact a little nose heavy.....I own the H9 33% Cap with this same setup (engine and servo) and have my 2 reciever batteries (2700 NiMh) at the rear edge of the canopy, and it balances OK for my kind of flying (actually a rear CG).....FWIW