I've had my share of elasmos die from transit (only once in transit itself), so that leads me to believe that our methods of acclimation aren't yet perfect - but my record has greatly improved with this setup:
Prep an appropriately sized (100-200 gallon stock tank/tub/pool) with freshly prepped saltwater about 40% filled, and bring it up to temp and salinity day before new sharks arrive. When they arrive, add a tiny bit of Prime and check water specs (temp, salinity, pH) of the shipped water, and adjust the tub as necessary to match the shipped water. Place sharks in tub, and after 30 minutes, begin drip acclimating them from their destination tank. Continue for ~3 hours. Depending on species and temp, add air stones.
Using that method, I've only lost one ray in the first 48 hours, and I think it was because of shipping; since the container leaked badly, and there was barely enough water in it's bag to cover it when it arrived, so I had to speed up the acclimation.