Here's a few pics of the aluminum shelf. The plywood one is the same principle but plywood and a skinny rectangular size (good for an iPad stand with a clamp holding one to the other).
The first one shows the shelf bracket with a disc of aluminum plate screwed to it with flathead screws. You could also use pop rivets but I used this. It also shows the captive bolts that hold it in place.
The shelf bracket is just one from the hardware store that says it will hold 100 pounds, and I have used these for other purposes that actually did hold pretty close to that weight for a full summer, 24/7.
The aluminum disc is from another defunct project that happened to be the right size to hold a laptop. Because it's metal, it wicks away heat nicely.
The bolts are the M8's or -10's that came with Ramsa WSA-200's, plus some washers and tight plastic washers that hold the bolts in place. Net new cost for shelf: $0.
This shows it in profile. There's two nuts on each bolt because the bolts are longer than they needed to be and I didn't saw off the extra, but I don't like bolt ends scraping on my hands. There are double the number of actual nuts visible because of reflections. Same with the diagonal brace.
The shelf part is spaced a few inches from the case because that's how it all fit together and this lets me have some space for hands or turn the laptop without jamming into the road case.
Here it is loosely screwed into the T-Nuts that penetrate the side of the mixer rack case, and the mixer is visible on the left. In use the bolts would be screwed tight, and the eyes give a good hand-hold and make it easy to attach and detach. The case is one of the EWI three door ones for rackable mixers with faders.
Hope this gives you some ideas.
