Very nice build! Is this really your first one??? Can I ask a couple of questions?

Did you use epoxy on the gantry as well or did you get it machined flat?

Did you have any problems getting everything square?

I see you have the z rails on the moving z plate, which is the better method. Is the z plate rigid enough with just the rails bolted to it? I wondered if C channel steel or a box made from ali plate would be better? (the rest of the machine looks super rigid)

(that's 3 questions! Sorry!)