I will try this model in few versions.
I will surely use 2 Hitec Hs-81 for rudder and elevator.
One Hs-55 for the throttle
and here are two versions:
-One standard or HS-81 for the ailerons,
-or two Hs-81s for ailerons.
I have seen and made( my Komacro) few japanese models. They use 6 micro 9gr servos (same as HS-55): 2 for ailerons, 2 for elevator and 1 each for throttle and rudder.
The fuel tank will surely be ligned up with the carb.I always try to have it this way in my models.

I have never seen an UCD for real. I hope that when I am going to sell some plans or kits I will buy myself one!!