The YS 120 is the engine I am running on the EF Yak 68" and it is very good. The extra weight helps balance the plane with out a problem, far better tha using PB dead weight.

I am finding that the 16 x 7 APC is about right for freestyle and 17 x 6 apc for 3d. I also have an adrenaline 120 with a YS110 in it, As Bodyworks states the RPM and power output is about the same for both engines. I would however run the 120 at lower RPM as it is not as rev'y as the 110. I would prop for about 9000 to 9500 on the ground. One thing though I find that the 120 is more torque-y than the 110 and as such has less trouble swingging a bigger prop.

You will need to run 20% or higher nitro fuel though to get the best out of any YS four stroke. I have used 30% but don't see the need as 20% has plenty of power.

Hope that helps

Kris