Just passing on something I did a few days ago to the Suzuki/Kappa bags, which I think makes a big visibility improvement. The sidecases have two plastic lenses (one front, one rear) that are basically nonfunctional but remove with one small phillips screw from the inside. The rear (red) one has a white plastic liner; the front (clear) one is just backed by the black saddlebag plastic.
I found a suggestion for removing these and backing them with reflective tape here:
...this link works about half the time but has nifty photos and stuff. I got a small sheet of Scotchlite high-intensity silver tape, used the white liner as a template, and stuck it behind the red lenses. Much improved rear visibility.
There is a guy in Oklahoma who sells this tape on eBay, all the time, in all colors - search for a seller named "doublewow." One small sheet usually sells in his dutch auctions for about $3, plus about 60 cents to mail to you. He also has a bright orange version, which I think is perfect for the dummy front lenses on the side bags - you can use the plastic inserts from the rear lenses as templates for the front ones as the shape is the same. Just be sure to cut the same slots in the reflective tape that Kappa cut into the white plastic, so it will conform to the curve. I'm sure there are other places to get this tape but Google didn't come up with very many, and most online merchants want $7 or $8 to ship it UPS, when it's basically the size, shape and weight of a postcard.
I don't have the Kappa top box, mine is a Givi E46, but I will be getting more tape for it too. Under the big red plastic lenses on most Givi top boxes is a sheet of silver-colored plastic - which is reflective but not nearly as reflective as the high-intensity Scotchlite.
With the enhanced reflectors, a Hyperlite, the brake-light kit in the Givi topcase, and a couple PIAA high-intensity 1157's in my tail light, you can pretty much see the rear of my Strom from adjoining states.