I have been flying my Ultimate and have to say its probably the easiet 3D plane to fly. Ill get some pictures and such soon.
I am running my FPE 3.2 with a mezjlik 21x10 and its really the perfect combo. I dont think long servo arms are needed for the ailerons and on high rates the plane rolls incredibly fast. At 6.5" from the leading edge it will hover and 3d no problem. I was flying around in harriers a lot today and elevators into hover transitions. Ill shift the CG just a tad rearward and call it a day. I had balanced it to begin with using a Menz 22x8.

I would recommend triple rates if you have the ability. The first rate is a low rate, second high rates for all surfaces, and third a rolling circle rate. Getting into the harriers and hover it would be nice to use a lower rate on ailerons and once in them I would like rull rates on everything with a good amount of expo.

If I had to decide what to put a 50cc engine on, it would be the Ultimate. I have flown the 28% planes and they awesome, but this thing just sets into 3D moves solid. It might just be a little more fun to fly than the 260

FWIW an engine larger I think would just ruin the sweetness of the plane. Using lithiums and a 50cc engine you will have a sweet 3D machine.