I wish I had a manometer.
I have no idea what my mill is set to and I don’t care. I care about the grist, not the gap. It will differ for everyone depending on their system. 20 years ago I set my mill as tight as it would go and I’ve never changed it.
Here’s a great podcast that is counterintuitive and recommends going to higher gap settings. I’ve taken mine to .045” and seen my efficiency rise but also a bit less consistent.
http://masterbrewerspodcast.com/079-brewhouse-efficiency-for-the-small-brewer