Huh, yeah, i see the problem. Have you tried enabling VSync? That should make sure the frame rate doesn't exceed the monitor refresh rate, even without a lock.
Another way i would attempt (speculating without knowing the particular hurdles of course) is a config file entry that allows changing the lock before starting the game.
Or set the lock to something high (like 240 or 360 fps) that will still prevent it from running at absurdly high rates.
Just ideas. If you already tried that, sorry for yapping.