My guess would be that the second Hopper would need to be completely disconnected from the internet, or at the very least on a completely separate internet connection.
I used to have two purchased Hopper Duos. Each Hopper Duo was connected to a separate satellite dish. (One on Western Arc, and one on Eastern Arc) So, there was no physical connection between the two Hopper Duos in this installation. However, they were both connected to the same WiFi network.
When I would purchase On Demand movies and download them to the hard drive of one Hopper Duo for later viewing, those events would also show up in the Purchases folder of the other Hopper Duo. I could not actually play those events from the other Hopper Duo (I would get an error message every time I tried.) So, each Hopper Duo's Purchases folder contained a mix of all Purchased movies that had been downloaded to either Hopper Duo, but each of those events was only playable on the Hopper Duo where it was actually stored.
(To Dish's credit, the above situation was not quite as bad as it may seem. All events from the opposite Hopper Duo were tacked on at the bottom of the list of Purchases. So, at least they were organized. Once you get to one event that won't play, you know that every event below that won't work, either.)
I can imagine similar issues occurring, if two Hopper+'s were connected to the same internet connection, regardless of how the Hoppers themselves are physically connected to the satellite signal. Simply isolating one Hopper on a separate dish likely wouldn't work.