I have had two major claims on UPS. Both claims were for broken stocks and I got estimates to replace stocks. The estimates were for more than the insurance amount and they paid the full amount plus the shipping cost and I kept the guns. I shipped one gun and the other was being shipped to me. In both cases the guns were inspected, and the packaging found to be sound. Payment in each case was made to the shipper.
In reality neither gun was properly packed. They were double guns shipped fully assembled. They were in hard plastic, foam lined cases. I never ship doubles assembled now. I wrap the barrels and the stock/action separately in bubble wrap, then put each part in a triangular shipping tube. The two triangular tubes are placed back-to-back in a rectangular box and taped securely. I have never had a problem with this method.
I buy my boxes from Uline. Total cost for packing materials is about $6.