The Mystery Guitar Identified... (sort of...)
Hey, you guys are great. Ask a question, and a couple of days later there comes the answer!
Another Guitarz reader, Paul Roub, very cunningly went straight to the source and asked the folks at the Rock 'n' Roll Hall of Fame, and they told him that the SG with the Flying V headstock belongs to Tim Sult of Clutch.
The picture here shows the Gibson logo quite clearly on the head (note also the Les Paul style pickguard), but I still don't know if it's a one-off custom jobbie or a "frankenstein". Perhaps now we know whose guitar it is, a little more digging might answer some of these other questions.
Thanks, Paul! Nice one.