Looks like very good pc interface to control cnc machine, I would like to try with arduino mega 2560
with independent dual end stop on Y axis gentry with 2 independent stepper motors on both rails of Y axis.
It'll be great if when in normal operation y axis and let's say y' as slave axis run as a tandem,
but when homing they home as separate axis to square of the gentry, with two separate end stops
or home switches on both y rails.
I see the 4th axis control on the interface but it should have some setting to run as a linear or rotary axis and if chosen as a linear and is slaved to any axis, it shouldn't have any separate control in the user interface.
To confirm, we do have firmware for dual axis homing on our Nighthawk controller, not sure how this can be implemented on a standard GRBL controller. If the MegaX dual homing works go that route. Great discussion here! :)