I wonder if it is the physical size of the servos? I cannot get the reccomended JR4131 as it discontinued, so what would you suggest? the 4131 had a rating of 6.5kg which does seem rather a lot for a DF. I only used Futaba 3001's for the all flying tailplane of my Paul Grey Hawk.
JR servos are physicaly smaller than futaba so which JR would you use now?
Big T