Indeed the screws stick out a bit, but they are well below the playfield with the playfield down and thus have no relevance to any decrease in clearance. On the other hand using an adhesive tape does decrease clearance X2 (both sides) and side mirror removal for any reason is not only difficult but has caused damage to wood sides and side mirrors when removed.

Some producers also provide or recommend felt on the playfield edges. This has been a disaster when the felt pulls of and the felt adhesive gets all over the mirrors and playfield. If you fear scratching your side mirrors when elevating your playfield, why not put some paper between the playfield and mirror before raise the playfield.

I have removed standard side mirrors to install colored mirror sides and was able to reuse the standard mirrors on another machine as original screw mounting permitted ease of removal with no damage to the sides or mirrors. The screws are very small and do not require any cabinet drilling for installation as they self tap into the wood through pre-drilled/cut holes in the side mirrors.

Side mirrors for the money is one of the easiest and inexpensive ways to add some life to your playfield.

The design of the side mirror is such that the mounting screws should be below the playfield and an interference as you describe should not occur.

Indeed there are differences in cabinets that become greater with time. A cabinet that has had the leg levelers not properly set can induce a warp in the cabinet over time as well as just changes in climate, storage and other factors associated with a unfinished (inside) open topped box. This is evident if you see deep scratches in the cabinet top insides associated with playfield elevation and return. Oddly you may see this on only one side, and indication of cabinet warp. Again this can be caused by improperly adjusted levelers.

Please send an email to the pinballsidemirrors.com site indicating your experience with the screws interfering with the lowering of the playfield. Customer support is important to this vendor.