Hello Al,
You're welcome. Yes, your understanding is correct. There is no chance of making contact with anything.
As far as squaring, If you make your target adjustable you can make minute adjustments in the target position, loosen the gantry and square to the target. Mine is easy to adjust, because my target mounts in the 80/20 slot. That gives it infinite adjustability. Another method can be used if you have to have a fixed mount position for the target. Just make slots where the target mounts. As long as you mount the target close to where you need it, the slots will give you a limited degree of adjustability.
I'm looking forward to seeing what you come up with.
Merry Christmas & Happy New Year!
Gary