I was thinking about adding a center piece, but I'm not sure. The problem is that the trim is not two sided. One end is thicker than the other. If I put it down the middle, I'd need to find a new trim piece.
If I order up the fans, I'll let you know for sure, but I was going to mount them for sucking air out too. Two on the sides for drawing in new air, and two up top for sucking it out.
Are those pics in your thread?