[bojan]

When astro-modifying my Canon cameras, I also removed the frosted focus lens.. resulting in much clearer and brighter image in the viewer, which proved to be helpful in aiming the scope.

However, the eye relief is now strange - i need to position the eye precisely and away from eyepiece (that was not a surprise..), which is not easy in the dark, so I thought to polish the frosted side of the focus screen lens and put it back in the camera.
Does anybody have experience with plastic lens polishing, what did you use, and how did you ensure the polished flat surface remained flat?