The tail section on my fastback is a great storage space. I have a good quality folding tool kit that slides in there perfectly. The case is semi-soft, and uses a zipper to secure it self closed. I used some thin closed cell foam sheeting to ensure that all of the sockets, screw driver bits, etc. stay secure in their elastic restraints. I added another layer of foam that has cut-outs for a small adjustable wrench, a small pair of vise-grips, and an emergency clutch lever.
I also have fitted a small set of hard bags that suit the bikes styling very well. I made custom mounts for them that bolt up to the mounts of my Bruce Chessell package rack. In the right hand one, I carry a quantity of zip ties, a cigarette lighter outlet adapter, and a tool roll that has a variety of tools that the other tool kit does not, including BSW wrenches, spark plug wrench, allen keys, electrical tape, and even a butane powered soldering iron with solder. There is enough room left over for a spare set of cold weather gloves and a jacket liner, for cold fall night rides home.
For longer trips, I also carry a small electric air compressor, hence the cigarette lighter adapter.
I have a small tail bag on my parcel rack that I put my documents in, as well as a hat, mask, spare glasses, cellphone charger cable, and a few small bungie cords.
The left side bag is reserved for occasional cargo: small shopping trips, an overnight bag, or whatever.
As a result, I rarely use my LH side cover to carry any thing. It is kind of a PITA to get on and off with the Fasback tank (the rear of the tank has to be lifted to allow the dzus bracket to slide outward.)
Hence, I can do a few nights on the road (staying in cheap motels) without feeling like a gypsy caravan, or having to resort to a back pack.
FWIW