My biggest recommendation with that kit would be to turn the motor so that the head is at 9 oclock when looking at it from the front, with the exhause exiting on the bottom of the fuze (with pitts style muffler). The stock config blows fuel all over the junction between the fuse and the wing and really makes a mess for clean up.

As to the Rudder, I enlarged mine a little, but what really helped knife edge for me was to move the CG back. The recommended spot is VERY conservative. It can be moved over an 1" back without getting touchy at slow speeds.