I am planning to make the Butternut Blondies from the whole-grain baking book. The recipe calls for dark brown sugar, but I only have light brown. I also have molasses. Can I sub in light brown sugar with a little molasses? How much of each? Any idea about how to do this by weight? I much prefer to use weights in my baking. I know that I could just use the light brown sugar, but I think that the dark brown would give a richer taste, and would like to use up the molasses since we are moving soon.