Small closet containing air handler in center of ranch style house with hall way to bedrooms. What are advantages/disadvantages of a short duct from air handler to ret. grill in closet wall? Is there a problem with no duct and using a large filter rack on top of air handler? The closet space would be a return plenum. I can cut a return opening through one wall to a bedroom, no duct. The other two bedrooms could use return grills cut through the wall into the hall way. This would keep return ducts out of unconditioned space.