This will be interesting. I will be following the progress since I am doing something similar. I am doing this: K40 12x24in rebuild (In Original Case) but with some modifications. I have a Cloudray laser head that needed a custom 3D printed piece to hold it in the right position, so I added a couple of holders for two line lasers for an aiming crosshair. In fact, my order for the parts I need from Openbuilds just shipped today.

 

I use metric as well. The math is so much easier. In my mind I can picture what 0.5 mm is, my brain just can't wrap around dividing an inch into 1000 smaller increments.