From a concerned Southern grammarian:

It’s not “y’all all.” It’s “all y’all.” “Y’all” = You (singular) “All y’all” = You (plural)

My apologies to all y’all.

UPDATE:

Yall is both you: singular and you: for small groups. All-a-yall is for larger groups (roughly 8 or more)

Becoming confused.

UPDATE 2:

In SC, we use “you” for singular and “y’all” for plural. Simple and unambiguous.

Room spinning…

UPDATE 3:

Sorry to be contrary but in Texican “y’all all” is perfectly acceptable as in, “Y’all all be careful not to tump over that cooler full of beer.”

“Tump?”