Hey Kaos, I also have the RD8000.. I did not install the servo arm as
Airtronics shows but have both facing the fuse.. I've had no problems..
I forgot how I set it up on the ailerons, but I now have it setup for
spoilerons( up movement with flap switch) It will work the other way
(down) but you have to change the flap switch position when making the
adjustments on the Ail./P-F channels on center(+/-) and EPA settings...
It was not to bad when I set it, I did have to go to the man., and I think
I also called Airtronics for some help:-)... On the Elevators I use 2
channels ELv./ 7... which works better than a "Y"... If you still want to
use the "Y" you should but a servo reverser wire/connector<-?? so as to
get the proper mechanical advantage on the linkages to prevent flutter
problems and losing the plane because of it.. IMO I would just go with
the duel channels... Much better:-)

One more thing on using 2 channels for the Elev... The Airtronics manual
states when using dual channels(7) for the elev. it will disable the switch for
the rudder mixing for coupling on K.E.'s.. Rud/Elev. and Rud/Ail. mixes...
But atleast on my radio that was not true, I still can use the switch to turn
the mixes on/off... Hope this helps getting your Radio/Plane setup!! The
UCD is a blast:-))))))))))))))