I think there's way too much overthinking going on with these rivet gauges and all. If you're doing a slow build, you're going to pound something like 14,000 rivets. Are you going to put a micrometer on every one, drill out the ones that miss the spec by .001", or what?
I used the rivet gauges on the entire build, to give each rivet a quick check...rivet won't go through hole? Check. Rivet won't pass under slot? Check. Next. I could do a whole row of rivets in less time than it took to write this.
If it would do either, then take a look...is it smashed too flat? If only a little, and the diameter is > the hole, probably best to leave it. If it's smashed to **** and gone, probably best to drill it out and do it again. Same for the hole...if it's sloppy in the hole, then it's probably not driven enough. I'm after a "snug" fit, where it just barely won't go. But if it's much bigger than the size of the hole, just *go look at it*. Is it severely over-driven, or is it acceptable.
Are there a few less-than-perfect rivets on my plane? Sure. But there are probably fewer boogered-up holes and oversized rivets from making a marginal rivet situation worse by drilling it out. Haven't fallen out of the sky yet, though.
You're going to drive a lot of rivets. If you get obsessive over thousandths of an inch on every one, you're going to be building for a loooong time.
Just my two cents. Take it for what it's worth.