There's a whole lot of room inside the fuse of the Ultimate to move things around if you want or need to. With a G-62 conversion I would think about placing the ignition battery as far back in the fuse as I could. Perhaps even consider li-polys for receiver and ignition for a lighter over all weight. Having them on the tray under the wing could work well. Another option is to construct a light weight tray that will fit just aft of the wing saddle behind the normal radio location, close to the cockpit floor. That would require opening up the bottom of the fuse covering, though.

I know that Tom doesn't care for this and recommends against it, but placing a single rudder servo in the tail helps quite a bit. Of course you could place two lighter servos in the tail for peace of mind instead of one heavy high torque servo