Well, I had extended discussions on the phone today with both Claude of Freedom and Jay of DMC, and I gotta say, the sidecar community is AWESOME!
Everyone I've spoken to is so damn helpful and informative! I guess we're a small community, and everyone seems to help each other out!
So, Jay convinced me that the Sportster subframe kit he sells is as close to a bolt-on solution as you can get. Along with the rolling chassis sidecar frame he sells, and the miscellaneous struts, braces, and clamps, etc. the complete setup can get me rolling for a lower initial cost than anything else on the market.
I think I'm gonna place an order soon. There's a build time and shipping time, etc, but it's getting stinky hot in Florida, and wrenching in the garage becomes more attractive than sweating out riding. With any luck, I may have something on the road when it cools off next autumn.
I plan on designing and fabricating my own utility/cargo options for mounting atop the frame, and maybe, just maybe, building my own tub someday. I'll also keep my eyes open for a used tub that might fit on the frame. Beater Velorex's seem to come up for sale from time to time, and I might be able to get an older one and discard the running gear, and just use the tub.
With any luck, this may turn into a build thread, or at least a "bolt together" thread...