I don't believe there's a canon reason why you can't have two magi taking advantage of one's metamagical prowess and the other's task-specific abilities. Certainly, I rule that you can. One mage makes the box; the other mage fills it. The exception is Open the Intangible Tunnel which, as written, creates the connection from the caster - a variant could of course be invented at the cost of an extra magnitude or two, though I'm not sure why you'd want to do so.