That’s exactly how I’ve set everything up for as long as I can remember. Measure the spring pressure, shim to within +-.020 and run it. I am a hobbyist and my tools may not measure as closely as someone with nicer stuff. I have two spring checkers and both have a scale that is hard to read down to the “pound” level. On this set I wondered how far guys really go. Your “hair” and my “hair” may be different by .010 or .020. Really that’s what my original question was. Here’s a better way of asking it, what’s the smallest spring shim you buy?