I can remember seeing Eric Haydock of the Hollies using a Burns Double Six as a bass (he also used a Fender Bass VI too)
Hank's latest Burns 12 string on the tour didn't sound too exceptional on the DVD- pity! Not like his original D6 on that old video clip of What'd I Say...
Regarding tension, there is also the question of MASS - those six bass strings in the courses may not have quite as much tension as normal concert pitch guitar strings, but their mass is considerable...a hopeful experiment could turn out disastrously!
Bill, for goodness sake, stop procrastinating with finishing that Strat 12 string!!!!
If you don't finish it soon, I demand that you remove the neck and send it over to me in Adelaide- so I can quickly knock up a 12 string TELE!!!!!