1 – Can’t stop thinking if it would be possible to install a second switch anyway? Or is that what you just said?
Connected so that the signal that keeps the gantry moving continues until both switches have broken the circuit.
It’s not the proper way to think but I’m new to this and I guess if it would be that simple, it would have been done right?

2 – To install 2 reference “pieces” from where the gantry position on each side can be measured.
So once in a while after homing the gantry I can twist one of the screws manually to set the gantry square and then turn it on again.
Would that work?

3 – I could let both ballscrews be driven from the same motor but I guess that would require a belt and with that I would loose some of the precision.

4 – What is the downside of squaring it the crude way besides that it feels… Crude?

5 – Would it help a bit if I choose 400 step motors instead of 200?