AltMill Table Crossbeams

Are the crossbeams on the AltMill a standard aluminum t slot profile? If so, is there a name for it? I have plans on using regular square and rectangle pieces but noticed the ones with the lip and holes for table mounting in the instructions.

If not, are these something the fine folks at Sienci would be willing to sell me to make my own table for my Longmill? :slight_smile:

Thanks!