In our 171, there's only a small wire bundle for the radio.
I used a coping saw to make the opening, a template to make the door (imperfectly following the ceiling curve is the only thing that I'm really unhappy about), softwood from a board (half inch thick as I remember it, the Pod's in storage) for a flush fit of the door and stained for a good match, tempered hardboard for a floor, two small hinges at the bottom, roller catch latch and a small hook to hang stuff on temporarily and to grip for opening the door.
It's a useful modification, we use it to store 3 or 4 rolls of paper towels and some knapkins and other light stuff. I'd include pics but I haven't been able to figure out how to size to fit the requirements.