I have the UCD powered with a Saito 100. I realize its over powered but after seeing a couple UCD's flying with this combination at fly ins I felt this was the combination for me. It turned out I made the right choice. I have over 50 flights and due to the excess power I experience no over heating problems. Our field elevation is about 700 ft and I use 15% nitro. It has unlimited verticle but the caution is, and as mention in other replys the UCD is not intended for fast flight. It is built light and to some degree is fragil. The control surfaces are large and at high speeds can exert destructing forces. In summary I think for most pilots, the Saito .82 would be a good choice for the 40 size UCD and you'll be happy with it. Let us know how you make out.
K.O.