I played around with an old cargo net that I had installed in my previous owned MotoVan. Seemed to be a perfect fit for an overhead storage option. After messing around with the mounting strap configuration, I was able to keep it tight and even with the top of the ROPS bars, so it won't hit rear passengers heads....if there are folks back there.
Last time I had my nieces in back, I noticed that the rear seat belts were hardly effective. The fold out buckles stuck up too high and the belt didn't even touch their hips. If they pull them down, the metal brackets dug into their hips. When the girls feel asleep, the cross-shoulder strap didn't touch them hardly and their heads would hit the rear shoulder bolster (the metal bar on the rear of the dump bed). It sort of bugged me that they weren't as comfy in my machine as they were in their dad's Yamaha Wolverine X4 that sports bucket seats. So, I ordered up a set of standard 4-point harnesses from eBay ($45 a pair). I had to cut the top mounting straps to use them as a strap-style instead of the bracket bolt-on style mount. I removed the top seat pad, and routed the straps around the steel bracket behind it, routed the straps to the center of the pad, and reinstalled the pad. This keeps the straps centered, and ensures that they go over the kids shoulders instead of around them. Plus, the straps are lower than mounting them on the top bar of the flip-up seat. The lap belt was simply bolted to the same place the factory flip-up brackets were bolted. Additionally, I keep two garden kneeling pads ready, and cut two pieces (about 10 inches long) of that black pipe insulation (same stuff from between the bed/seat back) and that covers the shoulder bolsters so I don't have to worry about their heads hitting (not that the 4-points would allow them to move much now). I keep the seat pads, and bolster covers stored in the under-seat storage tote beneath the drivers seat. The rear seats fold down nicely, and the belts should more effectively hold young passengers. I am going to order two sternum straps and shoulder pads just to increase comfort further. And, if an adult sits back there, they can either adjust the straps looser to fit, or simply loosen them enough to not even use the shoulder straps.
Storage....We can always use more, right?! And as many have found, storage that is safe from the elements and dust. I'm a sucker for Pelican cases after seeing how robust they are during my time in the Air Force...so I took some measurements and ordered a few. The Pelican case, model 1650, is the same height as the bed rails and I can fit one perpendicualr in the bed, or two running parallel. I will most likely just use one because I can easily mount and secure it down with lashing straps through the handles. This allows me open and close it without removing the straps and allows room for the soft cooler I have for the machine. After taking some more measurements, if the rear seats are up, I can slide the case back onto the tail gate. The Seizmik XD10 bed extender will fit perfectly for this setup, so I place one on back-order and they're expected sometime in early June.