I see no reason why someone with equivalent ability like Joe Calzaghe can not go from SMW to fighting a small Heavy Weight. Calzaghe was P4P no 2 in the world, he would have easily made the transition.
Calzaghe has retired so it might be a bit hard. Jones JR and Toney moved through the ranks successfully ah but wait that's not the point of this thread is it? It's yet another Yank having a go at Calzaghe, ain't it?