There's also another option, mounting mirror blades (of any thickness) onto the actual playfield rails so the blades lift WITH the playfield out of the cabinet, therefore no scraping issues.

This means the left and right alley rails need to be routed thinner (or better still, fit thinner rails) to allow the thickness of the mirror-blade to fit in snugly and then secure the bladers in place with short screws into the wooden rails.

putting it out there  ;-)
MM.

This is a valid idea as well though just checked my CFTBL and the ramps go over the side rails so this idea may only suit certain games. This concept would suit an Iron Man for example as the ramps and ramp support brackets are mounted 1-2 mm from the rail edge. Another thing to watch here is the screws that hold the rail to the playfield - would have to watch that the screws are not to close to the outer edge as once you trim the rails down you might expose the side of a screw and possibly weaken the mounting.