The aluminium angle you appear to be using to attach the gantry sides looks a bit flimsy. It can bend quite a lot with forces parallel to the Y-axis. Are you intending to reinforce it? Or perhaps you are mounting the gantry some other way...

Your workshop is looking almost as tidy as mine!

What's in the background of the 7th photo looks ideal for a wind turbine lattice tower :naughty:

Edit: Forgot to say, almost done the ballnut mount.