USPS API Shipping not working

I have my site setup to use USPS API for shipping and it seems to be connecting to the USPS server because I'm getting prices from them. My problem is that the correct shipping method isnt being applied. I have every product setup to have a weight. Most are 1 pound. I'd imagine that if an order weighs less than 3 pounds, it would only give you the option to choose that shipping option for less than 3 pounds (ie small flat rate priority). Also, if there is an order that is, let's say, 10lbs., there shouldn't be the option to use small flat rate priority but instead only the option of large flat rate. That is what is happening on my site when any order is made, all the shipping options are available. Someone can get cheaper shipping if they choose it which is not good. So I have all the products with a weight and I have the default values in the USPS calculated values but it doesn't seem to work? Any ideas?

I am running MarketPress 2.8.8 and WordPress 3.5. I also had to switch back to my weight rate method since this isn't working