Not sure if it would work for you, but I have Jb weld a stud in the hole and used a nut and washer to snug up. This work great on shovelhead head exhaust.
Here is my block grinder. many years ago I posted picture of it when photo bucket was around. I found a cabinet an estate sale, a 1930's medical cabinet made by A.S. Aloe company.
I going keep an eye on this thread. I have the same issue. That picture looks exactly like what I am dealing with. I only have this issue from the kitchen sink to where it ties into the rest of the waste plumbing I re pitched the line as it seemed to have a flat section. My guess so far are...
Looks like you will have a nice shop soon. Myself would only put a few on a motion sensor, then have to rest on a normal switch. Reason being if for some reason the sensor ain’t detecting you ( under a vehicle, behind some equipment). You will end up in a dark place. Good luck.