Jami,
If you were starting from zero, the trim tab would be a contender, but ...
Given that you already have a pendulum gear to my design that you say works very well, it seems to me that for the least amount of new work and the most confidence in the end result, you only have to make a new mounting frame that is wide enough and long enough to fit around the new rudder. That avoids stepping into the unknown with the RHM, and probably getting worse performance all round from the trim tab.
Don't be afraid to tilt the frame up a bit, so that servo blade trails and the vane leans forward a bit - say 2 - 4 degrees. This will make it easier to get the servo blade clear of the rudder.