I have a Protege .60 ARF that I train students with and fly for fun. It has a Thunder Tiger GP-61 engine and 12x6 APC prop on it. It's a wonderful primary trainer that is smooth, stable, and easy to fly; on full rates however, it is nimble enough to fly the entire Sportsman Pattern schedule.

If you want to slow it down, I'd recommend trying a 12x5 or 12x4 prop instead. That should allow the top speed to drop without allowing the engine to wind up too high. A 3-blade prop isn't necessarily slower than a 2-blade prop, it's just that certain 3-blade props like the Evolution trainer props are designed with a very shallow pitch.