[JRTJH]

Our 27RKS has the same type of cabinets for the reefer and the microwave. (However, they are located in different areas of the RV) In ours, there is a cabinet above the reefer, it is "short" in that it doesn't go all the way to the trailer sidewall. Behind it is the "reefer stack" that vents out the top of the trailer. I'd guess that the cabinet space stops about 8" from the side wall. In ours, the space above the reefer is a cabinet with a door on it.

As for the microwave, in ours the space behind the false panel is open to the cavity with the microwave. You can remove the 4 square drive screws in the microwave faceplate and pull it out (the microwave is bolted to the faceplate and it comes out as one unit) to see how yours is constructed.

I knocked out the false panel and built a spice rack in the space.