Anyone figured out Multi Box shipping?

Anyone know a good way to have CS Cart determine if X number of products can fit into the smallest USPS Flat Rate or Regional Rate box, then cascade to larger boxes depending on the size / number of items in the cart?

Essentially, I'm trying to figure out a way to avoid Priority Mail and use the cheaper, multi-box, shipping options. My store sells many different items in various volumes and would greatly benefit from this.

I'm thinking about having a system coded which take the dimensions of each product in the cart and verifies the smallest flat rate boxes all products will fit in, I haven't found anything like this thus far. I cant even imagine how much it will cost to do something like this…