Don't let anyone tell you that the OS .65LA is a low power engine. In the 2003 Model Airplane News .61-size engine comparison, the only prop on which the OS .61FX out turned the OS .65LA was the 11-7.

I have 2 of them and they are really good engines. I like a 12-7 prop.

I also had 2 Sig 4*60s. It's a big plane and the build-it kit seems to be heavy. I don't know about the ARF. I had my two powered by an OS .91FX and a Magnum .91XLS. Both these engines are built in .61 size cases so you get 50% more displacement at no extra weight.

Another thing, if you build any of the 4*'s, you need to cut off 1 rib on each side, enlarge the rudder and elevator. The roll rate is pretty slowwith the stock, long wing. It will roll better and you won't notice the difference on landing. The rudder is hardly big enough for good knife edge or snap rolls.