The system you describe is not a bad one, as long as there is a block attached to the end of the rotation arm to reduce friction. This set up gives you a 2:1 mechanical advantage. You can increase this to 4:1 by shortening the line so that the ends are under the tramp. Tie a small block to each end of the line. Now tie a line to a convenient point close to the cleat on the hull (tramp lacing might work) and run it through the block on the end of the first line and back to the cleat. Do the same on the other side. You now have a 4:1 mechanical purchase (a 2:1 cascade on a 2:1 system). This is used by quite a few F18 sailors. To control slack you can rig some blocks on the line that runs to your attachment close to the cleat and run the bungee from these blocks in a big loop to the corners of the rear cross bar under the tramp (using a couple of small turning blocks). Use thin bungee or else it will tend to pull the rotator back when tacking or in light air conditions.

Chris.