Magnum / Asp 52 FS are a tidy little engine that are reliable (well mine have been) have a couple of Thunder Tiger 54 FS which go well upright or at 90 degrees, they don't like working inverted. Also have a couple of Saito 72 FS. With this hobby as with just about everything in life you get what you pay for and you can do a whole lot more with a Saito 72 down the track than you can with a 52 of 54 size FS motor. It is all personal preference but my PC9 flew with the 52 and the 54 four strokes (that is about all it did) but with a 72FS in the nose it flies with authority and will do all of the moves. For my money pay a little extra and have a much more versatile engine. You can fly a trainer with a 72FS in the nose you just don't need as much throttle to do it.