I fabricated the larger TV shelf with sturdy lightweight ready-made shelving and decorative brackets from Lowes. The ready made shelving is in the home organization section of Lowes, not the lumber section. I made it a couple of years ago.
The 24" floating ledge crown moulding shelf was purchased ready made about a month ago. You can find them online but I just saw some on clearance at Michael's a couple of weeks ago. I ordered mine online from ennospace.com so I could get a close match to the other wood in the trailer. Crown moulding shelves are a pretty easy DIY project if you have the tools. I was on the road with my trailer when I started that project so I ordered the ready-made shelf.
The flush mounts need to be mounted the same distance apart on both shelves and both walls if you want them to be interchangeable.
I used adjustable flush mounts from Rockler.com to attach the shelves to the walls. They're similar to the ones you can get from Trailmanor, only the "adjustable" (2 hole) half is smaller. See attached thumbnail.
http://www.rockler.com/product.cfm?page=346
Due to the narrow size of the edges of the shelves, I attached the smaller adjustable half of the flush mount to the shelves. Depending on the setup of your shelves, you could attach the adjustable half to the wall, which would mean you only need to drill 2 holes in the wall. I attached the adjustable side to the shelf edges with wood screws.
I attached the 4-hole halves of the flush mounts to the walls with 3/4" long mollies with machine screws, and flat head sheet metal screws. If I had it to do over, I would use well nuts with machine screws for the aluminum wall. Anywhere that the mating parts of the flush mounts slide together, you need to use flat head screws. Any screw head that protrudes will interfere with the flush mount mating, so I used 2 mollies in the lower holes and 2 sheet metal screws for the upper holes of the 4-hole side of the anchor.
I got all the anchors and screws at Lowes. At Lowes, well nuts are in drawers with the other specialty-type hardware (not hanging on the wall).
This is an easy project but you really have to "commit" to it, because you'll be drilling holes in the walls and the holes for the anchors are about 1/4".
Betty