I've always liked milk crates for storage; ever since I was a hippie and used them for my LP collection.
They are good for the AI because they're easy in-and-out, easy to carry, stackable, lightweight and hard to overload.
This bin replaced our roadside passenger seat and is much better company than any passenger we've had.
It uses the seat bolts and is quite solid.
It nearly holds as much as the back end of our EXT and provides precious counter space for food prep, a Keurig and an induction cooker..