Having read this thread through, I was inspired. Lacking Paladin's creative genius and ability to work with metal, I went with the cooler idea. I went to Walmart and started looking around, and here's what I came up with:
5 gallon Igloo cooler... $18.88
Black Nylon stuff bag... $3.96
2 light duty lashing straps... $6.62
Flat black spray paint for lid... $0.96 (I hope this sticks, long-term)
It makes a great back rest, which has really helped me deal with the wind pressure on my chest. I think I will stuff some kind of pad in the front, as the vibration through that hard plastic makes my back itch.
Also, I took all the handles and cupholders and junk off the water cooler right there in the Walmart parking lot so I could bag it up and carry it home (take along a phillips). They had a similar cooler with a screw-on lid, but the handles were molded into the shell. The bag, when drawn tight, holds the lid on securely.
Thanks to all for the great idea. I hope the photos will help alleviate any trepidation other newbies like me have about adding to their Savage. It was easy, extremely inexpensive compared to factory-made motorcycle luggage that I looked at, and (I think) more versatile. When removed from the bike and separated into its original components, I now have multiple useful items instead of one fancy trunk. A laundry bag, water cooler, and tie-down straps.
That's enough out of me.
-Jason