I've seen two different sleeve thicknesses on the Supersport/lightning, so you may have the option of fitting a thinner sleeve if that turns out to be the problem.

One thing with the cocking lever is that it is not properly profiled from the factory, which means it digs a track in the sleeve.
Easily remedied with some dremel work to the lever, just make sure you done take off too much, just enough to clear the sleeve.