I'm using a SK .80 two stroke which works well but I'm at 600 feet above sea level.
Kangke sells these engines. They are at the following website.
http://www.atsrcplanes.com/skengines.htm
They have a .90 for $99.77, the .80 for $89.77

My .80 engine calls for a 13x6 prop... I'm using a wide 14x4 APC, you need torque, not speed.
Mine will pull out of a hover nicely, but not excessively fast. I've seen IMAC planes accelerate
faster out of a hover. You may want to go with the .90 at your altitude.
The U-Can-Do is designed for 3d with these large control surfaces. Do not fly it fast.

The rudder doesnt need a real high torque servo if you use a 5 cell receiver pack.
Since I'm using a 2 stroke, I put rudder servo under the wing & use a pull-pull system since my engine is lighter.
I did not add any weight. Forget the cowl, mount the engine upright & you will save yourself alot of headaches.

Also, sheet the fuselage on the inside with very light plywood (like 1/32 inch) in the wing area. This is a weak point.
I've had to replace my fuselage.
This is a great flying plane that can be flown very slowly in a high alpha position. Do not fly it high speed.
I've done a parachute, had the plane snap to level flight & had the engine continue on to the ground.
I've done an elevator all the way to the ground... this is hard on the fuse & causes the fuse to break at the wing.

For landing, my tail seems to hang down so I burb the throttle a couple of times to keep the speed up and the tail up,
it's easier to fly it down to the ground than trying for that perfect 3 point landing.