Hi Bryan, thank you for your detailed feedback! We're glad the tub cover meets your needs and appreciate your suggestion about a drain plug. It's great to hear how you use it for transportation and ice cream storage. We'll consider this idea for future improvements.
When we use the freezer, we will tilt the freezer sideways to slowly drain off some water so it will not spill. Then you can add more ice and salt. It is good to have some brine (water & salt) in the tub since that helps transfer the heat (coldness) to the ice cream can. Just make sure the drain hole is never plugged, or you will have disgusting salty ice cream.
Thanks again for sharing your thoughts!