This is going to require at least two posts, you may want to give me a day or two to get the second half of the data together before replying, unless you want to guess what the results are.
So I had to figure out why exactly I couldn't get the 30mm carburetor to run right. First off was the idle. I sent a picture of the carb intake to a buddy of mine and he commented that the slide travel was being restricted by something.
Based on earlier conversation, this carb is likely too large for my application, so I didn't see why allowing the slide to go lower would be a problem if I already had an idle issue.
There was a ridge along the edge that was keeping the slide partially raised. It would be easy enough to add back later so I ground it off.
Afterwards the slide nearly came to rest in the bottom of its slot.
Started up the buggy and for the first time I was able to adjust the mixture screw and get a steady idle. This change I am quite happy with and it hasn't given any issue over the hour or two I've put on the engine since the modification. Idle is the least of my concerns now. Next up is trying to figure out how to get a richer condition at WOT. Previously I posted that, even with a large main, I was still lean WOT.
The issue had to be one of two things - Either the slide was not coming up far enough at WOT to sufficiently get the needle out the way of the main jet, or the slide was opening up sufficiently but the air velocity was not fast enough to draw enough fuel from the venturi. I did a ton of testing with data logging and think I've finally figured it out.