Just extend the soffit above the rest. There’s no real functional gain for what you are proposing with that many cabinets in the kitchen. Additional storage at must have a step stool to access is outweighed by the mess and expense, when there’s already plenty of storage.

Thank you. The island is not in front of the fridge, it is only in front of the pantry. And I really appreciate you mentioning the fridge door opening - the fridge I picked only needs clearance of 4 inches between it and the wall, so we put filler there. But this is a hot button for me as I spilled something in my rental fridge recently and had to swing the door way out in order to get the drawer out! Thank you!

They went out of business recently and someone else bought them and reorganized, I think. They're also an import line from Asia (China?). Most import lines are VERY limited in sizes. Most don't offer the 39" upper wall cabinets. If you want frameless find a Shiloh (ECLIPSE) dealer in your area. www.eclipsecabinetry.com

First, use a flashlight to see if there is ductwork, you may need to remove the grill. It is pretty common for people to treat any enclosure like ductwork. If there is no ductwork contact the company and discuss solutions with them. If there is ductwork it likely needs to wrapped with insulation and so the cabinets should be removed and the duct wrapped. If you can't remove the cabinets lining the bottom of the cabinet with ductboard or some rigid foam insulation will help although it is an inelegant solution. If there is no ductwork, you can add ductboard under the cabinets by piecing it in through the vent opening and gluing it to the cabinet. It will be a tedious and annoying job but will improve the problem. ETA: to piece in ductboard measure a piece that fits exactly into your inside cabinet bottom. Shorten it for the toe kick (typically 3.75") then cut it in half. Apply adhesive to each piece and feed them in and adhere them. Use a broom handle to ensure they are adhered. If you want to add sides, cut them to fit (Usually 3" if you are using a 1" ductboard) and adhere them to the sides.