JUst a suggestion......add another 2x on the front of the shelf. That way nothing is hanging over. Then add a 2x above, a couple uprights, and some doors. Build it out flush with the existing soffit above. Take a look at fellow member XcYZ's soffit build in his garage.
If you go to the trouble of making a garage look nice, tuck the boxes and other stuff out of sight. Plus just have an open shelf collects a lot of dust. If you just run a bench grinder for a little bit, the dust gets airborn, and will settle on any horizontal surface. If you mow the lawn, and dust at all will head straight for a garage if the door is open. And everyone knows that an open door is a huge vacuum that will **** any dirt in. Just look at leaves in the Fall. They patiently wait at the front of a garage door just planning their escape from the big world outside, only to seek sanctuary inside the confines of a nice garage, where they will hide behind anything remotely close to the floor.
Here is XcYZ's thread
http://garagejournal.com/forum/showthread.php?t=45022