Hi ok to be totally honest I can't remember exactly what we canned it at but it was probably around what you are thinking (also with quart jars). The main thing is to get the PH low
enough. We used test strips that measured between 0 to 6 in 0.5 increments. If you search for something like kombucha PH test strips you can find them.
Something that I didn't mention is that we employed the ancient technique of leaving the sap out in freezing temperatures overnight. We then removed the ice and used the unfrozen liquid for preservation, making for a slightly sweeter concentration that balanced nicely with the sourness of the acidifiers.
Also a note on the plants: Lemons were fun but of course not from our region so we just did a few jars of that. Hibiscus was for sure the most cost effective herb. The sumac-ade was the most
local to us and involved foraging which is what we enjoy best. But all were totally delicious. We also added other herbs to some of the brews to make some extra special concoctions:)
We haven't been able to tap for the past couple winters but we actually just finished our last quart from that original batch this past fall. Still super good!