If you envisage that the likelyhood of a nasty crash is high then supply your stepper PSU through a cut-off circuit with switches at the ends of travel, if you use a multi-pole, double throw relay you can E-Stop your spindle controller and E-stop your control software at the same time.
No matter how kind your hard stops are if your machine winds into them hard you're no better of than if you hadn't fitted them at all,
- Nick