I saw a recipe for sourdough pancakes on King Arthur's website, and it called for two cups of liquid starter. I have about 1/4 cup left over when I refresh my firm Maggie Glezer starter, but nothing like two cups! I did make half a recipe of the pancakes and they turned out OK (they also called for baking soda, so that was safe, I guess.)
How does going from firm starter to liquid starter go? Two cups sounds like an awful lot!