I am having the problem that customers are being allowed to select Media Mail for products that are not Media Mail appropriate. I can't figure out how to tag Media Mail appropriate items as such. This seems like it would be a part of allowing Media Mail to be selected at checkout. As far as I can tell, you can't tag products as Media Mail. I need to be able to differentiate products as Media Mail acceptable and not Media Mail acceptable, or the Media Mail option at checkout is mostly useless. It will allow customers to select the reduced Media Mail rate, and then I will have to ship the items using a more costly method.