Depends on how you want to fly it. I have a Saito .72 in mine, and I love how it flies. Now, if I were to buy an engine just for this plane, then I might go with a .90 4-stroke, but as it was I had the Saito on hand. I was pleasantly surprised. It obviously does not have unlimited vertical, but it pulls up nicely from level flight, and does all the aerobatics I want from it. It is in no way a disappointment with that engine.
-Ron