I never set a "certified minimum" for mini-BOS here in Seattle, though it may have worked out that way due to way the tables were made up.
We generally had a Certified or higher in each triple. Occasionally, it was 2 Recognizeds and a novice or pro, but there weren't many of those.
In case anyone is interested, here's how I set up the judge pairings/triples:
1) I had to make sure that no one judged in a category that they entered.
2) Ensure that those judges with lots of entries got placed first, regardless of rank.
3) Ensure that the Nationals and higher were spread out across all the categories in the session.
4) Ensure that a Certified judge or higher was in every pairing/triple. 2 Recognizeds together was ok, too.
5) Ensure that Certified Mead Judges judged the Meads (and Ciders).
6) Ensure that each Apprentice and Rank Pending judge is paired at least once with a National or higher for at least 1 flight, but preferably more often. If not, I paired them with the most experienced ranked judge available.
7) If they checked the preferred/non-preferred category lists when registering I favored those preferences. I'm happy to report that not a single judge had to judge a category they marked as non-preferred, and most got the categories they marked most favored.
Hope this makes sense.