Questions about default packaging size and shipping rates?

With the recent updates to USPS rates adding fees for box lengths this is something that needs to be addressed. Before we were able to go based off weight alone because the dimensions of the box were not really an issue for us. But when we have to add $15 to ship a poster sized box because of the length alone, well now we have problems. Most products fit inside a shoebox, so that is our default package size, when someone adds something is very light but long, we have to eat the $15 fee. I know this is more of USPS complaint and we do have other options but Shopify should have an easy way to just be able to set a certain box size for a product with a simple priority list. It doesn’t have to be complex. If this product is in cart then use this box size, otherwise use the default. At this point we don’t care about the UI, give us basic functionality.