Just installed a fold down spice rack in our 21C. It was too large to fit on the galley side, so I put it on the driver side under the tv connection area (we have the full size cabinet, not the two drawer stack).
Install went ok, but I have a couple of tips:
1. Used 8mm bolts clear through to the inside of the cabinet, with large washers to distribute the weight. If you do this try to get small star washers that will fit in the slot in the rack to prevent rotation of the bolt head when tightening the nuts.
2. Not thrilled with the latches to prevent it coming open while traveling. Will probably install small hook and eye screw catches.
3. The rack is too large, but could not find a smaller one. Good place for bird and mushroom id books. This is the rack on Amazon:
https://www.amazon.com/dp/B0BJZS7M1Q...roduct_details