This question was prompted by Scott's comment on this tournament report: http://apps.magicjudges.org/forum/topic/30167/

How do you (try to) deck check the top 8 of your local tournaments? I find that most of my tournaments run 5 rounds, and by round 4– when the top 8 starts to take shape– people are already IDing. If they're playing, obviously, I can check them. In round 5, those who have to play for it are often bad candidates for deck checks, as it probably gives the checked pair an advantage in the stupid ID-if-the-9-pointer-loses minigame.

I'd like to help keep people from cheating their way to a T8, but it seems like a crapshoot when I'm checking, and my current algorithm (random undefeated table) doesn't necessarily lead to good T8 coverage if my r2/r3 checks don't do as well in subsequent rounds.

I assume that if a 5 round PPTQ can have people ID by round 4, we're talking aboyo a small PPTQ
In that case, I'd use the recommended method for local events instead:
“For Top 8 at your local events, my suggestion is to get the players started playing - everyone benefits! - and do a quick sideboard check during game one. That addresses the concern about pre-sideboarding but doesn't delay the event.”