Thanks
I did think of the switch falling into a hole but the arc it travels is very small and lands exactly where the torch would, I have been messing today and tried tight spacings, near-edge etc and all worked fine, if it would work with the torch, I think it will work with this. A true edge-start might be tricky, don't know yet, never done one.
The sliding Z is staying and i will be moving the limit switch wiring to the e-stop circuit as the limits do nothing when g28.1 is running, luckily I wired every switch with its own cable back to the control cabinet.