I have seen servos that are upwards of 170 grams and produce 40kg of torque.
I am betting these would make awesome pull pull rudder servos for something like a 50cc Yak.
Question is would they also work for aileron and elevator servos as well?
I could be wrong but at 50cc size I would not think the difference of a 150 grams total spread over a few servos would make too big a fuss. (I mean you could strap a couple of GoPros to one and be fine, and they weigh more than that.)
I would however be nervous about the sizing. (Apart from the rudder one. That one is a gimmie. Plenty of room and solid wood)