I was just thinking about that adjustment last night. I was going to slide the gantry to the driven end of the x axis, locate the ball screw bearing block there, then slide the gantry to the non driven end and get the position for that screw bearing block. Suppose great minds think alike lol.

Great advice about getting 25mm plate. Does that mean it would be safe to remove 15mm of material? If I don't need EcoCast then what would be suitable 6082 plate, 5083 plate or 6082 flat bar. Also how accurate does the 10mm plate that goes behind the gantry have to be? sorry for so many questions.

I basically was reading in lots of forums that 15mm profile rails would be plenty strong for all axis, but never thought 20/25mm would be better for filling spaces between z plates.

Originally I was going to make the z axis the way I'v drawn, then use a working machine to mill out what we are discussing for a version 2 machine. Thanks for offering, I will pm you about your pricing once I've re drawn it.