Max # of items per shipping method?

Trying to get my shipping options set up. I have a the USPS flat rate priority small box. I can only fit 2 of my products in there at a time. How can I set a certain shipping option to only allow a certain amount of items allowed per shipping method? Thanks

Someone might correct me if I'm wrong, but the max items doesn't work for USPS. I know this has been reported in the bug tracker, but I don't think anything has been done about it.

Hopefully someone will tell you that I'm wrong.