Advance and transfer slots

If you are not getting an off-idle tip in sag at 10/12 degrees, AND, the trans does not bang into gear, then the Idle-Timing and fueling, is darn close, if perhaps a tad rich.

BTW, synchronizing the T-slot to the mixture screws, to the idle-timing was never My own idea, It's been around forever.

Just how big is your cam, and
I assume you have an automatic, so
About where does it stall, ballpark; and
WHAT carb, and
does it have a 4-corner Idle system?
Single or dual plane?
What is the operating elevation.

At to your "hot soak" situation.
"Hot soak" implies after the engine is shut down, and obviously ignition timing would have nothing to do with that. So Ima guessing you mean something else.