what I’d do is drill the m5\m6 holes with the shapeoko then drill tap the holes.
I think for my wasteboard drilling the holes by hand (electric drill) took about an hour. If I recall I have about 100 holes. Tapping took less then 10 min using a m5 drill tap in my dewalt drill.
The main reason for recommending this other way is a cnc milled waste board is very expensive and let’s remember it’s a waste board it’s devastating when you hit your shiny new waste board with your mill…
Unless your producing many boards the cost won’t come down (I looked at small production runs). The actual frame mounts don’t actually need to be all that accurate (2mm deepening the size of bolt) as you have to square your machine. By using the shapeoko to mill the holes you get the best of both worlds, lower price tidy look and feel.
I did my whole board by hand and I wish I used the shapeoko to mill the holes - whilst mine are at 5cm spaces I can see some are slightly off - granted it makes no difference to the work holding.
Something to think about when making one for the xxl is what type of items are you milling? If only big things you need less holes. In my eyes the main benefits to the aluminium base is the ability to stick things to it, and the ridigity.
I do allot of small items under 15cm and I’m considering making a small nomad style board that bolts onto normal wasteboard.