The external Zamp SAE Plug on the side of Oliver directly connects to the Batteries.
That means the suitcase (portable) solar panels will need their own controller as it doesn't connect to the Zamp Controller inside the trailer and used for the solar panels on the roof.
If you were to use one of the Zamp suitcases the waterproof controller is included with the panel, and they come with the cable for connection with the Zamp SAE connectors and/or battery alligator clips.
The Zamp branded Solar Ready sidewall port (SRRV) found on the Oliver are completely compatible with any Zamp portable solar panel.
Not all SAE wired ports and portable briefcase solar panels have the same positive and negative connections.
The polarity may be reversed when the solar panels connect with another brand of SAE quick connection extension cable or solar charge controller.
Shown below is a ZAMP connector.
This is this one is used to connect between the wall of the trailer and a Zamp Solar Battery Maintainer panel.
(I'm including it so you can see what the SAE connector looks like and see that in a ZAMP connector they have RED wire the rubber covered connector and the black wire going to the exposed lug.) This protects users from contacting a + lug if they plug the connector into the Solar Panel first.
The typical SAE plug (below) is reversed, and has the RED wire connected to the Exposed LUG, and Black goes to the rubber covered lug.
As others mentioned, it's possible to find adapters from the Zamp SAE sidewall connectors to other brand connectors so it's not a huge issue...just a bit of research. In fact, Zamp sells the polarity reversing plug below for $9.99. (On sale for $4.99 at this time).
So ...if and when you select the external panel...just make sure to get one that has it's own waterproof controller, and the proper connector/polarity adapter.