[bob deluke]

First Of all Flat, why a floor grill? All kinds of crap will find their way into the grill and duct. Any chance to wall mount the R.A. Grill? You’d probably have to patch the floor, so extra $$$. R.A. Grills are relatively cheap at plumbing supply house or big box stores. The 20x8 duct is pretty standard in the industry, again at plumbing supply house. Snap lock fittings on duct easy to put together. Need a takeoff installed on existing R.A. duct to accept the 20x8 duct. All toll, about 4-5 hours worth of work, couple hundred for materials. Typical diy project. I think this outfit is looking to hit a home run with you. I’d be looking elsewhere. Did they do a load estimate on existing furnace/ductwork? How did they arrive at the conclusion your return was too small? Whomever does your work, I’d insist on a load estimate calc. It determine duct size. Man, these contractors are charging Porsche repair shop prices!