Subbing coarse for medium grind cornmeal

I would probably pulse the cornmeal in the food processor to a finer grind and proceed with the recipe.

What does coarse really mean? I have cornmeal labeled for polenta -- that's really coarse. I have just plain cornmeal which is whole grain and stone ground -- I think of that as medium. Then I also have 'corn flour' which is still whole grain but ground to a complete powder. Your 'coarse' might even be Bittman's 'medium.' If not, you could let the cornmeal soak in the liquid ingredients first, then add the wet ingredients and the rest of the dry ones, and bake as directed. That would remedy somewhat the textural issues. Then again, coarse might be delicious and you could go with it by adding some crunchy, chewy ingredients.

I would use the same amount of cornmeal called for in the recipe, but expect a coarser, sandier texture in the bread.