Just wanted to put a final post on this thread for anyone doing a future build and uses this for reference.
The knockouts described above work perfectly. I bought a 13/16 & a 9/16 and both worked beautifully to make the recommended holes in my 20ga Blichmann Boilermakers, and were a fraction of the price of the Greenlee counterparts.
Follow the directions and grease the screw! And maybe most important, spend the $4 on the right kind of drill bit for the pilot hole. Cobalt is what you need to drill through stainless. Took me 45 minutes to drill the first hole with a regular bit. Less than 30 seconds with a cobalt bit. Right Tool, Right Job, Right!
Again thanks to all who replied to my inquiry.