Oh Sweet. Yes, I’ve had enough of z-offsets and such in the 3d printer world. I will definitely add your z-probe. Thank you!!!
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A few learnings from my installation:
Diamond core drills will give you a nice round hole that doesn’t care if you hit aggregate or not. Plus, you don’t need a hammer drill to drive them.
Hammer drill bits WILL do weird things when they hit aggregate. Drilling a small pilot hole (maybe 1/4" using the nice bits sold for those “screw into concrete” screws) helps a LOT getting the hole where you want it. Drill it out with a medium size drill bit, then go to full size. I finished with a diamond core drill to clean up/straighten.
If you go from solid with the diamond core drills you will need to break off the core once or twice. I’ve done this on a granite surface plate making 5/16" holes 2" deep. A well anchored/stable drill helps this process a lot. Cooling/flushing water is nice to have but not 100% required for concrete. Especially if you consider the core drill bit to be a consumable and just buy a couple extra…
With a closed bottom anchor (or an anchor that you plugged the bottom on) you can blow the holes out carefully and glue them in with JB Weld. I’d trust that more than the expansion type anchors.
My installation uses swimming pool cover anchors which have an M14 threaded hole in them. I use a long M14 bolt bottomed out in the anchor and a PEX pipe spacer to get the anchor points all at the same height; roughly 4" off the floor. I custom printed belt ends to match the M14 bolts.
I messed up on one of the anchors and set it at an angle. Some day I may drill it back out and re-do. Maybe. 
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I have an anchor that has a bit of a gangsta lean. So far it does not seem be causing any problems.
I had one of those too… Take your frame measurement and height from where you actually put your belt and it won’t matter.
Plus one for water to help cool diamond bits, less silica/something dust, so, longer life for the bit, and you.
True! If you don’t hit big aggregate, you might get half a hole out of a dry bit. With water in the hole you just keep on truckin’ Since you bought the 6 pack, use one per hole
Tip: stop ever 30 seconds or so to let the water fall back down into the cutting area.
A wet/dry vac to clear out the hole regularly is handy.
On mine, for reference, I hammer drilled in steps to clear out the guts: 3/16", 3/8", 1/2", and 3/4" IIRC. I bought the one big one for this job, and the others were what I had laying around. I used the Poolzilla anchors with custom belt ends to fit M14 bolts.
Big aggregate lumps are a PITA. Sloooooow diamond cutting.
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