I have one room that is getting very little air off the main unit. It currently has a 6" flexible duct. I would like to increase the flow by reducting with rigid duct. The question is: Would I be any better off, or should I change the size of the duct? Increasing to an 8" would seem to help move more volume, or should it be smaller to increase the pressure of the air flow? I am also going to insert a blower fan that triggers off the main unit fan relay. Any suggestions?