Moki,

get the latest manual from the Tower website in softcopy and have a look at the CG.

Sierra11861,

the 61FX is too heavy for the power. Instead, get the 75AX...its more powerful and almost same weight. Or if you have the money go for a FS-91SII. This is actually lighter than the 75AX and since the UCD required inverted installation (I think) its more suitable. And it has plenty of power for the UCD 46. Just note that the UCD will flutter if you fly too fast so be conservative with the throttle.

I dont have the UCD but a Phoenix Models equivalent called Topstar 60. I tried without much luck with the inverted 75AX. Then I installed a FS-91 and lowered the tank. Since then its much better

Ameyam