a fully extended chassis on rails in a wall mount anything (frame or enclosure) is going to place an extreme amount of pull force on the wall attachment points.
I would personally not place anything but a static, fixed load into a wall mount.
equipment on rails is a lifesaver and, if you really want to do it, consider a freestanding enclosure thats designed to take deep servers, extended loads and has anti-tip features.
just my 0.02