CRE 6.4B2B Shipping Zone Setup

Need assistance setting up zones on CRE 6.4B2B to work with USPS shipping zones. Currently using shipping table but it is not efficient. We sell in both the U.S. and Canada. We are subsidizing shipping to Canada. Because we drop ship (we do not have inventory, we order from the manufacturer to ship direct to the customer), we are finding that we are subsidizing a lot of the shipping cost. A customer is paying $19.99 shipping for an order of $150, which is being shipped from 4 warehouses. Our total shipping cost is $30. We have had to increase our product pricing to account for this. We offer free shipping of $250 but would like to decrease this amount to $150; but only to U.S. customers. We have four stores but only two that we would like to see the change made for. Will provide the information to the successful bidder. Confidentiality is important as one of our stores has a unique clientele. Price is not the only factor in our decision, quick turnaround and good communication is as well.