Have spent the weekend drilling and tapping a scary amount of M10 holes in half inch aluminium plates, for the base. In the process discovering various issues. The oldham couplings were slipping on the Z axis, so I added some grub screws which has largely fixed that problem. Plus the nuts holding the ballscrews into the bearing got loose... which was not ideal! So had to take it all apart and tighten them up. If it wasn't for this though my forearms would be significantly more painful from tapping...

I also discovered that one end of my X-axis ballscrew supports was 0.7mm further out than the other and the ballnut, which might have been making the couplings work harder than they should. There is a definite wobble to the screw now...