Feeler gauges can fit in out of spec

So, now that I've removed and reinstalled the camshafts about five times, I can no longer deny that I don't know how to use feeler gauges.

The measurements I took initially ranged a lot (driving the crank, with the same shims, just on the second go-round, I was getting different numbers). I was able to determine that pressure in the cylinders was at least partly the cause. Knowing that, I was able to wiggle stuff around and get the largest clearance for each valve.

In many of them I'm able to get the .008/.203 gauge under them, but can't even forcibly squeeze the .009 in.

Since my spec says .08-.18mm, I wonder.. if .203 is the last gauge that'll fit, are the odds decent that a proper measurement is .178 (the next gauge down) instead?

What I would love for someone to say is "yeah, man, if you're having to push a .203 in there, a skilled feeler-gauge user would probably measure a .178. Even if .178 slides pretty easily, just run it. They'll all expand anyway."

So, anyone care to humor me?

Gaps very rarely get wider, if anything they get narrower over time. I never set mine at the tight end of the range, loose end doesn't worry me.

I sometimes see slight variations in clearance depending on if the cam chain is tight or has slack. Best to turn the crank only forward to keep the chain tight.

I can no longer deny that I don't know how to use feeler gauges.
In many of them I'm able to get the .008/.203 gauge under them, but can't even forcibly squeeze the .009 in.

Feeler gauges are tricky. You have to develop a "feel" for them. what you are looking for is a slight drag when you pull the feeler gauge out of the gap. Forcing a feeler gauge in means it is way to tight. You should be able to slip a feeler gauge into the space to be measured and slowly pull it out and feel only a slight drag to the gauge. If you feel no drag then go up a size. If there is significant drag then go down. They named them "feeler" gauge for a reason but in the case of valves go with a wider clearance if possible.