Hi,

yes, 60x60x4 is ok to make a good structure. Having in mind your desired work area. may be here and there you have to add small diagonals, cause my design is in fact quite minimalist and really is done best using 80x80 or 100x100, but when talking about machines that will do mainly aluminum. So you are ok with that.

No problem for the epoxy leveling, the pour is wide 40-45mm and deep 5mm.

You will go for aluminum gantry or from box section? If box, then you will need something bigger there.

Good luck with the build