With standard 3/4” box matetial construction, the inside of that would be 4”. That wouldn’t fit a coffee mug in it, and nothing at the rear would be ever accessible or cleanable. What you have described is creating a horizontal filler panel, not a cabinet.

agree with verbo. But u could do wine cubbies....if not, storage for saran wrap or small platters.

Get new cabinets. It isn't about "more expensive," it is about marginal expense. The doors are the most expensive part and the upper boxes aren't that expensive. There might be a 10% savings if you are lucky, it just isn't worth it.

Thank you both! We could potentially do wine cubbies in one spot as its not near the stove. On horizontal fillers -- I need to be able to attach 36" doors - Can those be attached to a filler? Honestly, the only reason I'm looking for the extra 5.5" is so the height difference between the 42" cabinets and the rest is not as high (looking to separate them by 6" instead of 12"). I may just have to bite bullet and pay for all new 36" cabs;-<!

a picture of your existing cabinets and what your refacing choice is would

If you do U-shaped boxes, move the cabinets higher, and attach the boxes at the bottom, you'd gain another 3/4" interior height. The stored items would be more accessible at that height, and you could use thin trays for small items, then pull out the whole tray when needed--think small spice jars or baking novelties such as cupcake liners and bottles of sprinkles, pill bottles, etc. Use one tall door, as you planned.