Check out the performance w/ YS 110 FZ

http://www.pedrofrigola.com/UCD3D&Stinger.wmv

I have tried several engines on my UCD3D 60:

Magnum 91 2-stroke w/ APC 15x4W: good power, but the throttle response is not good for 3D

Saito 91 w/ APC 15x4W: OK throttle response, just enough power to pull out of hover, but couldn't get out of trouble quickly enough, hence resulting in a crash and broke the wing.

Saito 100 w/ APC 15x4W: good throttle resopnse and good power. Plane flies very light w/ this setup, but idle surges due to high fuel tank and low carb position. Not sure why this wasn't a problem w/ Saito 91. Prolonged idle followed by throttle-up may quit, which happened to me when I entered a 5-ft wall after a long idle glide, plane went up and went down the same path, and remained the path 'til it meets the ground. Broke the fuselage.

YS 110 w/ APC 16x6: great power, awesome acceleration, enough to do tight KE loops. Only w/ this engine do I dare doing eye-level hovering. I did break the rudder like this just this week.

Enya 155R w/ APC 17x6: great power, response is so-so, plane flies heavy, and idles too fast to have a manageable taxi.

So depending on what you want to do. Saito 100 will fly it very well for the most part. Just mount the engine upright. For all-out low 3D, go for YS 110.