Drilling and threading the rail for a pair of M4 thumbscrews is easy, and they are easily removable.
I avoid SAE for consistency in my threaded fasteners, but IIRC 6-32 thumbscrews are super cheap and available since they were used for pc computer cases.
Incidentally, the locking screws on old serial connectors are 4-40, and lots of extended shaft thumb screws in 4-40 are therefore easy to get. One made my etx125 finder instantly removeable.
A button head screw can also be used for a never-removed safety, and its looks will not offend, but thumbscrews work great.
With either, buy the drill and tap set, usually very inexpensive, to avoid weak threads or broken taps (HD, Lowes, Amazon). Reverse the tap a 1/2 turn every couple of turns to clear the chips. Keep the tap straight, their hardness makes them relatively easy to snap.
I have been buying Irwin taps and drills and am satisfied so far. I avoid chinese unbranded on taps due to the unmitigated disaster of broken taps, tough to remove without damage.