Not that it matters now, but I consider the whole idea of screwed together extruded aluminum to be a very expensive way to do a job poorly. We use this stuff everywhere at my job, and it is constantly falling apart, stripping, sagging, rebuilt, rinse, and repeat. I would never use it for a machine base. We’ve done it here, and it invariably gets rebuilt with welded steel.
For an application such as something like a safety cage without any doors, it works decent. Put a door on it, and you may as well start building the steel version. Put any weight on it, especially weight that moves or vibrates and it’s worn out in 6 months.