Attaching X-Controller to Sideboard

I am nearing completion of the assembly of the 1000 mm X Carve. I have the X-controller all wired up and complete. Nothing in the directions say how to attach it to the sideboard. One of the assembly photos shows the bottom plate with four rubber feet, which are supplied, but there are also four corresponding nuts in the sideboard that I think can be used to immobilize the X-Controller. If I wanted to immobilize the X-Controller, what size (probably M5s) and length and head type would be used?

I admit that I am not answering your question … but I left mine unattached and it’s been just fine. Handy at times, even.