I added gap seals to the elevator of my model III to improve elevator authority. I would run out of elevator and could not flare because the stick was all the way back already. The gap seals made a big difference. Replacing/enlarging the tail surfaces is pretty major surgery, I think I would try the seals first and see if it makes it ENOUGH better.

I used leading edge tape from ACS, half lapped sticky-to-sticky then attached to horiz. stab and to elevator. Took about 10 minutes.