Well, with my Moki 135 etc (1350gm), ele servos up front, battery on engine box, throttle servo on engine box, a 66gm brass prop nut, its going to take 350gm on the engine box and 130gm on the mount (lined up with cylinder centreline) to balance it. Thats a total ballast (ie deadweight) of 546gm or 19.5Oz. Better than some, but still a sign of something wrong in the design or build. The stab halves seem to be foam/balsa, with maybe glass over it, and the fin also seems to be similar, which will add a lot of weight where its worst.
Curiously I have an ESM Katana (78"span, 2m), with a Moki 210 in it, servos in the centre, but behind the cg, and it needed a moderate amount of tail ballast. Its tail end is very lightly built though.
jp