I did some measuring today. I think another solar panel would fit in the back if you delete the TV antenna. Looks tight, but just possible. It would also require turning the panel mounting brackets around, which looked possible but I haven’t done it. Would make dealing with the mounting bolts a challenge, but should be possible with the right tools and dexterous hands!
Disclaimer: Until I or someone else actually does this, please don’t count on it being feasible!
A narrower panel (the stock one is about 26″ wide not including the brackets which in the “outward” orientation take 2″ or 3″ on each side) would make installation easier, and might also fit forward next to the Maxx Fan..
The mounting bracket. With it outward like this it makes the bolts to the rack easy to access. To conserve space on the rack, looks like you could probably turn it inward.