Does anyone have any actual experience trying to increase air flow in a 6" hard metal duct using booster fans? My dining room gets air from a 25' long 6" duct, but it only as two bends, one at the start above the master duct and the other coming up through the wall. The actual gas blower is 4 tons and should be enough, but the force at the end is weak. Were you able to get a better air flow?