We have found that without a substitute, the crust is tough and chewy. We
had a devil of a time figuring out what to add, until we took a "kitchen
chemistry" course and found that the missing part is the protein. We also
found that wheat gluten is wheat protein. We experimented with adding pure
wheat gluten to the recipe, and found it to make nearly perfect bread. I
believe it was just a level teaspoon, but it's been a while. I also recall
that the bread rose better, so we had to reduce the ingredients slightly to
not have the bread stick to the top of the bread maker.

G'Luck!

Mark