Glad I could help, if only a little. Reading over what I wrote before, I'm not sure if I was clear that for the cup of potatoes and 7 - 8 cups of flour I suggested, you'll need AT LEAST 2-1/2 cups of water. In other words, you can start with that much safely -- and you can also count on needing 1/4 - 1/2 cup more (at least).
FWIW, I sometimes add finely minced scallions or chives to potato bread. A touch of dill is another nice addition. So is a few table spoons of cottage cheese or ricotta. Potato/scallion/dill/cottage-cheese -- hmmm starting to sound like a Scandinavian, onion-dill bread. In fact, that's what it would be.
At any rate... you got me off my rusty dusty. I just finishing putting together enough dough for a couple of loaves of Struan bread. It's just starting on its first rise now.