Popped in a W11 (I think? 1.80mm tip, vs 1.40mm previous) needle, a 32 pilot, and tried 80 main (vs last attempt at 69, too lean up top, lost power).
The reason for the needle and main jet change: it was running rich at WOT at lower RPM, and lean up top. Now, this was news to me, but revalatory: according to Wobbly over at KiwiBiker, your main jet DOES NOT control WOT at lower RPM if it's in the ballpark - that's up to the needle tip diameter and needle jet! With a 260ish needle jet and 1.4mm-ish needle tip diameter, you end up with a huge annular area in comparison to the area of a 80ish main jet. Like roughly 5x the area. You get an extra boundary layer that slows the flow down a bit (the needle). Apparently you can pull the main jet out of the carb, and if your needle is right, you can go WOT up to some set RPM, at which point the main jet takes over and you'll get too rich.
This concept worked, quite well. FINALLY I got some heat in the pipe. Hadn't seen it exceed 450C, ever, before this. Almost got up to 700C at one point, with a good amount of time at 600-ish. Target zone is apparently around 650. Going WOT cooled it down a little, so may need to go down a touch on the main jet.
Definitely the best the bike has run so far. Will get a new video soon.