Is to remove the old box, and front of cabinet, and building the shelf, then putting the front of the cabinet back in place with removable screws.
Trying to get the look of the built in and still have the option of replacing the portable when needed.

I built in the old one as I felt the same way, wanting the beauty of the built in. But now see the real beauty of a fast replacement unit.

I know you know your way around, did you check out the Engle built in replacement systems? It's the same guts as the portable, same low power draw, but made to drop into a built in. They have one with the compressor attached and one with it made for remote install.

When you hit the Sea of Cortez, you will NEED a good working box! AND, the power to run it. Every bit of power you don't have to use pays you back twice.

Greg