Good to know, never heard of the hatchet cam, I'll look into it if I have issues when mine is installed/tuned.

Update:
After much reading and testing ideas to discover how to increase my idle A/F's up from 10 - 10.5, including increasing the idle air jet orifices from 1.10mm (stock) to 1.18mm, I found the cause of my issue yesterday.
Previously I had found best idle setting with the idle mixture screws turned completely in (basically closed)? This means that fuel must be entering the throttle bodies from the intermediate orifices in order for the engine to idle. However after several inspections, I could see that the throttle plates were correctly positioned at idle, with their edges covering the lowest intermediate fuel orifice.
Cutting a long story short, with the carbs back on my bench, I observed that the idle mixture screws with "cup"washers covering O rings restricted the screws from being fully screwed in, leading to the previous conclusion that the screws were fully screwed in - closed. After removing the washers and O rings, the screws could be screwed in an additional approximately two turns! I reassembled the carbs and installed them with the mixture screws turned open one full turn. After unsuccessfully attempting to start the engine, I opened the mixture screws one half turn and the engine started immediately. After adjusting further to best idle and allowing the engine to warm up, the idle A/F mixture gauge showed steady 13's - success!!
I have since learned that my Weber 40IDA's were original equipped with mixture screws that did not have these cup washers and O rings. Here are two pics of the mixture screws:Click to view attachment Click to view attachment

Hmmmm....very interesting and extreme diligence on your part. I will definitely check mine, as I also have low AFR at idle and do not get consistent LbI indications. Thanks and well done !

Interesting.. I actually need a few of those cup washers. Anyone know where to get them?

You can find a lot of the little parts at partsklassic.com

I do not believe you NEED them, other than for originality optics purposes. They have no useful function other than perhaps a little help to prevent the screws vibrating loose - unlikely with the springs doing this. The possibility of the intake vacuum pulling air through the threads is minuscule and I would judge as extremely unlikely be enough to have any performance impact. One source suggests these O rings were an attempt to show good faith to environmentalists - per discussion on PP

FYI....

There are also 2 types of idle jets used in the IDF's.

Are you sure your using the correct set for your IDF's?

The spring should compress and allow for the idle mix screw to bottom out. Only turn them in until they lightly seat. Don't go full gorilla with them.

I'm running same, just a bit bigger main jet on my 3.0, I also say leave it alone.
Getting better AFR from this point will be a game of a dog chasing it's tail.
Aircooleds need it a hair rich anyways.