I have some left over grain from previous batches that i am looking to use, at least in part. I am looking to make a porter which calls for 8 oz chocolate malt and 8 oz caramel 60, 8 oz special B, 8 oz black malt on top of the 10+ lbs of 2-row. I have some chocolate WHEAT and some carawheat left over. I also have some munich. Aside from "aiding in head retention, etc", what would be the differences (positive and negative) if I sub'd an oz or 2??