I subbed 1 3/4 c. of fine flour (first clear, I think it's called - some bran and germ sifted out) for 100% whole wheat in the body of the recipe, kept the biga 100% whole wheat.  The results were good, crumb less dense, whole grain flavour intact.

I also divided it into three pans instead of 2, which makes for smaller sandwiches and easier to slice bread.