I think I might be doing the same setup. The weight penalty is not that great and I can make up the weight difference in servo selection and RX battery. Something to be said about having stupid power. I have used the Saito 180 on the H9 27% for not so unlimited 3D. I can only imagine that I would get the DP Ultimate all together with the 180 and wish I had more. The engine weight difference alone is only is only a ounces more.

When you take into account that you have 1200 squares to work with you can sneak some things in. I am thinking mini servos for ailerons and throttle, and 5945s for elevator and rudder.

Its common sense that swinging a larger prop will make the plane fly better. I just wonder what else people are running besides the mez. 19x8. I imagine you could do a bolly 20x6 or something similar.