I found the basic recipe for this bread in Dan Lepard's "The Art of Handmade Bread".....and took a few liberties.
My white flour starter was 16 oz and I added a 1/4 cup of buttermilk, 2 tablespoons of honey and 2/3 cup of shelled pumpkin seeds. The result was two large loaves of tasty, chewy rustic bread. Lots of flavors with the rye and barley flour plus the pumpkin seeds inside and outside seem to be a nice addition.
The following worked up to be ~4.5 lbs of dough:
16 oz active white flour starter
1.75 cups water with 1/4 cup buttermilk
1 cup of barley flour
1 cup dark rye flour
2 tablespoons honey
bread flour to make a pliable dough
1 tablespoon course Kosher salt
2/3 cup shelled pumpkin seeds with more to sprinkle
Bulk rise took just over 3 hours with one fold at 1.5 hours. I shaped the loaves on parchment paper, let rise 45 minutes, slashed and misted loaves and sprinkled with seeds. Loaves were baked on a tile at 425 degrees F.