Deja Vu all over again You really believe what your first paragraph says ?
The high speed needle controls mixture below 1/8 throttle ?
IF airflow through the carb is too low to "effectively drag gas out of the Main fuel feed venturi" why would adjusting the high speed needle make any difference ?
Last paragraph..Set the high needle so the engine just starts to run rough at 2000 rpm ?
Contradiction maybe ?
I give up