Due to the base construction, there is now a pair of enclosed compartments in the base which I wanted to be able to access. There were two ways that I could do this. I could either cut an access hole in the side panels or cut access holes on the interior shelf. My main reason for wanting to reclaim the space was that it would be a perfect place to locate a power strip that that both tools would use.
In the end, I thought it would be easier to access the cubbies from inside the cabinet. But before working on the shelf, I installed a couple full-extension slides. The ones I had on hand were only 22", but they should be okay for a 26" deep drawer. I'll store a couple rolls of sandpaper for the sander in there. (Note the temporary back I have installed. I need to go cut a taller piece for the back.) I cut the long edge of the shelf openings with jigsaw, cutting proud of the line so I could flush-trim it afterwards. I cut the short edges of the opening on the bandsaw as close to the final location as possible since I would not be able to flush-trim up to the side. Flush trimmed and fastened in place:
I didn't want these cavities filling-up with sawdust, so the plan is to make some removable covers that will drop in flush with the rest of the shelf. I glued and nailed a cleat on each short end.
One of the sides will get a large hole for electrical cords to come in/out, and the space is plenty big for a power strip. I haven't quite figured out what will go in the other side, but its nice to know that the space won't be wasted.