I'm trying to sell through Miva heavy products that weigh about 400 lbs. Being based on the east coast shipping on the same item may vary from say $50 to Virginia all the way to $250 if shipped to Seattle. Is there a way with miva that I can for example split the US in 3 or 4 zones with different shipping rates? or is there a module available that I can buy and set shipping costs according to the states.