Ron,

I have both the 4*40 and the 4*60. I run a .46 in the 4*40 and the OS .61 in the 4*60.

Mine were kits so I don't know much about the ARF version. I love the way these planes fly and I would have to say I fly my 4*40 more than anything else I have. You don't need much runway for the 40 version so you can fly it just about anywhere.

I bulit both planes per instructions and haven't had to beef of anything in the kits.

Hope this helps.
Ed