OK, here's an update for anyone interested.
Today I started from scratch.
Checked all cables for free movement.
Set throttle at minimum idle and adjusted idle stops for .004 clearance.
Then closed the idle stop screws about two thirds of a turn.
Set the mixture screws open one and half turns.
Left the balance tube connected. Started engine and warmed up to operating temperature .
Carefully adjusted both idle stop screws to give a smooth running engine at desired RPM. I set mine at about 15 or 1600 with throttle pulled completely back.
Then I shut down and connected the Carbmate directly to the balance tube nipples.
Restart but do not idle the engine. Keep it above 2500 or so and run up to 3500 or 4000 . Adjust the cables to put the GREEN in middle at the most sensitive setting through these high RPM s This may take a few restarts and fine adjustments but it is worth it.
Remove the carbmate and reconnect balance tube.
My engine seems to now run smoother than it ever has and that is saying something!

After considerable time attempting to balance with the carbmate attached through ALL
RPM ranges I have come to the conclusion that it is more effective to get a smooth idling engine by adjusting the idle screws with the balance tube connected. My thinking is if the ide is SMOOTH that is more important than where the green light is!

Anyway did a few circuits in 30C Temps tonight and it performs super smooth through all RPMs.
This a long winded explanation that may not be by the book and may not work for everyone but my old 912UL likes it.
Thanks for comments especially from Mangy that really got me thinking.
Cheers
Don