How programatically choose between multiple shipping methods commerce_shipping?
So, this doesn't answer the question as posted but all I had to do was set my series of conditions for the Postal Code Weight method. My scenario had to Flat Rate Shipping methods based on specific products in the cart. What I did was configure the Rule for Commerce Shipping Postal Code Weight with two conditions, 1) that it didn't contain one of the products, and  2) AN and OR condition that it didn't contain a product. I also had to specify the conditions for the two Flat Rate Methods similarly, one had to have an exclusion targeting the first product condition.