I am preparing to start building my 2nd plane now. Like Everyone else I am going with the U Can Do 60. After watching a ton of various .60 size planes fly at the club it looks pretty clear that you need at least a .71 bare minimum even better a .91 if you really want a .60 size plane to be able to perform aerobatics with unlimited vertical capabilities. I am going with the .91FS engine. and am hoping I can contain myself on the throttle while I am learning so I dont make a super fast trip into the pavement. My teacher took the U CAN DO 60 with a .71FS engine through the entire advanced pattern with relative ease but it was a little sluggish vertically. As spaceclam said if you can afford the initial investment I think that the 4 stroke is the way to go. Its quiter, more fuel efficient plus it just sounds better. Very high COOL factor. OS .91FS Surpass is a little over $225,,, I have been shopping for a while now and watching different planes fly and it seems to be the best for the money in a .60 size plane.