definitely makes a welding table more useful by adding the ability to clamp things down flat without welding on the table. industry standard seems to be 16mm so that it will accept tooling from stronghand and other companies that make the clamps. if you decide to drill holes, I would suggest laying it out as precisely as you can. even a hole pattern on 12" centers will give you a lot of options for holding parts. you can always add more later. a mag drill would help a lot

hope this helps,
Jody