Elbow - Grades

I found myself really liking Elbow as I read about his views on grading. I liked the fact that he pointed out we don't have to assign grades to everything, and gave ideas as to alternatives such as rubrics, contract grades, and portfolio's. I thought the discussion was lively and it made me feel better knowing that we are all in the same boat; not really embracing the whole concept, but having to accommodate the system and give grades. I am still wondering whether or not I need to do my "grades" differently for math. Should I incorporate contract grades and portfolio's? I already do some with rubrics. But math is more concrete. I definitely want to incorporate writing to learn. So I have lots of things to consider and think about. Any suggestions?