I have a finished attic that currently has no supply or return for heat. The area is about 250 feet. I have located a way to supply area through a closet and into the attic. The issue is that I only have one way to get it up there. The return would have to be smaller. Could I do this and would one supply and one return be enough for this space. It is really not all that cold up there after insulating, and heat from teh main level, so I'm not looking to make it really warm. Just basically a supplement done right. Or do I NEED a return (I know its the best option, but is it absolutely necessary)?