put your servos as close to the cg as u can without having to add weight to the tail the plane will fly th best with its weight around the cg, but on such a small light plane you will have to comprimise a little to get it to balance. i usually install servos last, i tape them in place untill i find a good location to achive the desired cg. if you r battery location moves do this with the battery centered that way u can adjust the cg fore and aft after first flights to dial in the cg