Mark, good luck. Just be very patient - takes more than 5-8 seconds for a tuning action to take effect in this regime. I found that 7 turns out on the Low and 5+ turns out on the High would be a safe starting point.
Here's a latest video indicating that a good tune/cylinder balance can be obtained from this engine all all throttle settings if the carb is tweaked properly. Temps are now read off the surface of the Keleo manifolds near the cylinder exhaust port (sort of an EGT but not really).
BR.
Hector.
https://www.youtube.com/watch?v=9XVHvinfnog