https://www.thingiverse.com/thing:1023985
They snap on without removing the rails, I typically use zip-ties to keep them on screws are overkill.
With this firmware you just need to get the endstops close and you can fine adjust an offset to get it really precise.
This also picks up the Z axis before homing, I have it set to 10mm right now I think but usually that is plenty. A bunch of it is adjustable, which axis homes first, all at the same time, whatever.
I need to get a better video of it but, I kinda got stuck on another project at the moment.