I had to 3-D print my own carb to airbox boot/adapter, that worked great and if anyone needs one, happy to print and ship one.I drilled and tapped for the genuine Mikuni oil injector barb, was very careful, and that went quite well.So now I'm tuning, first, the bike runs much, much better. My original carb was just shot through. She now responds to the air mixture, idle set, etc. Unfortunately I failed to take note of what jets are in the VM by default... sigh. Also, the needle comes on notch two - I now have it at notch 3 (4 seemed worse). My symptom is that at 3000 RPMs, she stops being smooth.. at best I'd say it becomes a bit choppy. I'm not certain if it's lean or rich, just don't have the background/skills to know. I think.. it's going lean so I'm thinking I'll go back to notch four and then focus on the air screw.FWIW this bike is all original (except for this new carb), and in really great shape.Question: Anyone have any experience with this particular upgrade/install? any advice on jetting? I have a complete assortment too to facilitate tuning.

You can get a small shim / washer and slip it under the needle clip , to effectively have a 3.5 clip position .
Niche cycle or other mikuni distributors will likely have one .
It may , or may not , solve entirely your issue , but it's worth a try .
From memory it was .5mm thick .

Makes sense, question though - are these adjustments; the needle position, air screw, etc., are they that sensitive? The bike seems so much more crude than that.

It's all about finding a balance . It's not a major to give it a try , and you might find a happy medium .
If you don't try , you'll never know .