saito 125 definately! this type of plane should definately have a four stroke engine in it. for 3d you want to throw a big prop at lower rpm. maybe a 17 x 4 wide or somethin. long and low pitch slow and more tourque. a guy art our club ( popcan ) has a u-can-do with saito 125 and it flies awesome! i have a ys 110 in my showtime 4d 90 with an apc 16 x 6 and 25% cool power fuel. the ys 110 is a powerhouse...way more power than 125 and weight is good too....but they are expensive. i have seen the u-can-do plane with a 125 and it was awesome. ys110 would be more power but the u-can-do is 60-90 where showtime is 90 meaning u can do will fly on smaller engine and saito 125 is awesome.

just my opinion