Definately NOT a plug and go!!
The DOHC tanks are wider in the tunnel area and also a little longer than the SOHC. I'm in to building SOHC CHOPPERS so NOTHING is impossible if you have the talent and equiptment to do it yourself. You could ,cut out the tunnel of the DOHC tank/bottom of tank and FAB/WELD in new sections. Since you are going CAFE style you could reconfigure the aft mount and make it work.
But , consider this I'm the type of guy that WON'T be told "IT WON'T WORK or YOU CAN'T DO THAT"
Xnavylfr(CHUCK)