Yeah, I'd never multi-class to Sorcerer if I was a Wizard, simply cause I don't particularly care for the class, and see no point in hampering my spell progression w/ a far less superior class. But I always figured that casting level stacked, for purposes of Item Creation feats. So I take it a 4th level Cleric/ 1st level Wizard couldn't take Craft Magic Arms and Armor. And if not, how about if the cleric had the Spell Domain from FR.