Why — other than “that’s the size of the hole in the unit”— did you need that 96” x 32” duct anyway when a 56” x 56” square or 60” round would have carried the air with the same friction loss? It’s ...

Grab a duct calculator, read the fine print about round sizes and check out the fixed alternative rectangular sizes. Read that a 16-inch round at 201 square inches in area is equivalent to 15-by-15 ...