I've used the refinedcycle adapter (below) to stick on dual 5¾-inch headlights on my vt600.

That said, the dual 5¾-inch headlights don't put out as much light as my single Valkyrie headlight. I dunno if there's room up front to attach 2 Valkyrie-size headlights on a Valk. What diameter headlights were you thinking of using? And why?

