I am having the same issue and really didnt see any resolution. I have 2 shipping class. One is UPS for items under 50lbs and the other is for items over 50lbs that is a flat rate cost. When i add the 2 products to the cart, and go to checkout, it shows each shipping as an option, not both mandatory. so the customer choices the cheaper option which is not the case. the customer should see a UPS charge and a Flat Rate Charge. Please help