"fair to midlin'"

What is higher than "midlin'" in "fair to midlin'" ?

This from a July 2000 discussion: The word "middling" meaning of average size, mediocre size or quality, etc., dates from about 1550.

So the next step up would be...fair to super size?

I've always understood "fair" and "middling" to be synonyms, so "fair to middling" is analogous to "so-so", or "six of one and half a dozen of another".