As you know, our system only allows a single preorder item (though there can be multiples of that single item) in an order. We do have a workaround in order to meet free shipping. Just contact us and let us know what items you'd like to combine into a single shipment. As long as the total cost of the items exceed the free shipping threshold you should be good. Once we verify that the items meet free shipping you will place your orders and we will immediately refund shipping costs. Then, we place the currently in stock items in hold status until the preorder arrives, at which time we will ship everything together. We have tried mixing in Curbside Pickup, (even if obviously there's no way that could happen) but it's cleaner for bookkeeping if we refund the shipping at the time of the order.