Bob,
The metal would probably work well. I added 2 in (balsa) to the rudder of my old Sr Telemaster to make it handle better with jumpers but mainly to offset the torque from a Sato 180 on takeoff. I may add a balsa extension to my Meister rudder the same way. It takes a lot of rudder input to keep it going straight on takeoff and I have 60% rudder mixed with the ailerons to get it to make a better coordinated turn when flying to altitude with 3 jumpers hooked up. I thing a larger rudder would help a lot.
You ready for Somerset!! Any idea how many people are coming?
Jim