Customized USPS Shipping module for Shopp eCommerce plugin

Requirements: You will need to have a working knowledge of WordPress, MySQL, PHP, a basic understanding of shipping procedure, and be willing to look into the Shopp WordPress plugin ([login to view URL]). Goal: We need a talented programmer to help customize Shopp's USPS shipping module. Description: We're using the USPS shipping calculator for our store. We have a base shipping rate set, as well as a standard handling fee. But we sell differently-sized/-shaped merchandise. Posters, books, prints, and large canvas paintings - as well as small bottles and such. USPS charges shipping based on location, and weight. We can ship 5 8.5x11 poster prints together (around .56 lbs) - but after that it takes another package. We can ship 5 11x17s together (around .82 lbs) - but after that it takes another package. A poster tube takes 5 prints, and weighs around 1 lb. The rest of the stock is shipped based on weight. So - no matter what, if we ship a poster we will be charged around the same no matter how many posters are in a tube (max 5). The 8.5x11's can be shipped with the "by weight" items, but everything else is shipped separately. So we basically need the ability to put products in certain categories, and have the USPS module calculate the shipping weight based on number of items - depending on the category. Like, 5 posters = 1 box shipping but 6 posters = 2 boxes. It seems like a simple job, but we're not programmers - so we have no clue. You will have full access to the Shopp documention, the plugin, a demo store, and any source that you need.