skerste, it is possible to transfer recordings between the two Hoppers with an Ethernet cable. Both Hoppers will need to be plugged into power and have the most up to date software to make sure the process goes smoothly. This feature will only transfer recordings. Any timers or folders you have set up will not be transferred/saved.
The steps on how to complete an Ethernet transfer of recordings can be found here: https://www.mydish.com/support/products/hopper/how-to/manage/transfer-between-hoppers
The amount of time the transfer will take will depend on how much of the Hopper with Sling's storage space is used. Approximately 25% full will take 12 hours, 50% full will take 1 day and 100% full will take 2 days.