This Hangar 9 Spitfire has an OS91 4-stroke engine.
In this video you will notice that the engine begins to run very rich part-way through the flight, making for an unplanned landing. The exceptionally forgiving slow-speed handling of the model is well demonstrated by the fact that it doesn't drop a wing even when almost stalled.
This particular H9 Spitfire belongs to Jeff and he says it's a very nice plane.