Place pet body in freezer. Once frozen, ship to us in an insulated shipping container with some dry ice, following the rules of the shipping carrier. We also have Shipping Containers available. Large pets are a challenge. We don't have any good answers. The only two options seem to be to find a bigger container or else to just ship us the head. One option for a larger container is a plastic picnic cooler placed inside a cardboard box. It can be challenging.