Product add-ons should change weight of product
When you have product add-ons with an appreciable amount of weight relative to the base product, the total weight of the product that is added to the cart should be adjusted to reflect the additional add-on. If I sell a picture that weighs 2 pounds, and a product add-on, e..g, a picture frame, that weighs 1 pound, then the the picture and frame combo added to the cart should weigh 3 pounds for purposes of shipping.
The FedEx Extension just pulls in rates for the original product without consideration to the add-ons. Also, the Invoice and Packing List Extension generates packing lists that only show the weight of the original product and completely exclude the weight of the add-ons.
This to me is a major problem that should have been addressed before the plugin was even released.