I don’t have scale drawings and the PCB design is flexible, they cost like $1 for three so it doesn’t really matter, but the ones I have recently ordered for my ZY-T08s are 10mm, mainly because that’s the largest drill size my drill will take. I’ll drill like Old-Lumens did, leaving a shelf for the PCB to rest on, then an 8mm hole through for the wires. How deep I drill the 10mm part depends on the switch casing I find, can drill 10mm all the way through if a solution requires it.
However, I wouldn’t mind 12mm either as I have a 12mm PCB on the way for a triple XHP70 build where the host (Roche M170) already has a E-switch hole, but I got it without switch casing. If 12mm is a better size for E-switch cases I’ll just get another drill that can take 12mm drills and use that size for my ZY-T08s. I’ve posted in Old-Lumens thread asking what size drill he used for his.
How many I would need? Four is what I’d at least like to get my hands on, but could buy more as I suspect a few mining exploration friends will like the ZY-T08 once my driver and firmware is completed: Mod/Driver: ZY-T08 series conversion, MT-G2.