What would I do differently?

I’d start from the outset with an enclosure! I probably wouldn’t have gone for the long bed.... but I don’t think that was a major cost component.

I’d put the home sensors outside the envelope of each axis to avoid crashes. I was taking a puritanical approach that the supplier recommended end-on sensing, but my experience has taught me that the performance difference doesn’t worry me, not as much as inadvertent crashing the axis. That wasn’t helped by me using one control box for two mills, resulting in weird configurations that could result in the sensors being unpowered and subject to crashing.

I’d roll the x axis stepper towards the rear of the bed rather than the front. I believe there’s space there if drawn close to the bed. Y I’m happy with. Z I don’t really worry about so not much in the way of introspection there. Definitely retain the quill lever

I have belt covers on each axis now... 3D printed was easy.

Unspoken of here is the replacement of the bldc motor with a servo... a result of me blowing up the spindle controller trying to adapt it to support 0-10v operation. That is now commercially available from sieg in any case. My solution, not necessarily recommended, requires me to think of adapting the spindle controller pendant. (Another roundtuit job)

Part of this evolution is the chassis wiring isn’t quite what I’d intended, I’d plan that as bit more carefully.

There’s a sieg user group on Facebook which has a couple of cnc’d 2.7s, if you’ve not seen that already. Useful to see what others get up to.