Richard,
I love mine. I have had two good years of flying on it with an MDS1.48. The 1.48 pulls fine but is not enough for anything about Sportsman level. You might find that the 1.20 4C will fly the plane and allow you to do some aerobatics but anything above Basic will not be competitive. Dave flew his on a number of engines and recommends the YS 1.40 for it. YS puts out a powerful engine for sure. When I talked to him about the 1.48 he said that it should be fine and it has proven so.
I met a guy with an RCS 1.40 on his and he was able to get around the sky and have some fun but that was it. The extra weight that gas engines add don't do the plane any good.
The Saito 1.8 is a great engine for this plane as well.
Some suggestions.

Mine flies great. I have had a couple of dead stick landings and will contradict what Dave said a little. While you shouldn't try to float the bipe to the ground, fly it in, you'll find that it has some VERY nice glide and flair characteristics that make landings very easy. I have a friend who built the CG Ultimate several years ago and the MINUTE the engine went dead, that thing dropped like a rock. I was prepared for that to happen with mine but that simply wasn't the case.
Enjoy!!!