shelves

I just did that same mod using 3" L brackets.  Like you, I was hoping the bracket would be mostly hidden by the valance, but found that they stick up about an inch or so above the valance due to the window.  You might be able to cut an inch or so off the bottom of the bracket, although that might mean you would only have one hole through which to secure it to the wall with a screw, which may or may not be a problem.

As far as studs, you're just drilling into the side.  No studs.  You can use a drywall anchor to make it more secure.  I had some on hand and was planning to use them, but found that it seemed sufficiently sturdy with just mounting the screws into the walls.  We're not going to be putting much weight on the shelf, so it seems quite sturdy to me.

Hope that helps.

Another option is Molly bolts.

Beachmaster,  I posted this elsewhere, responding to some general questions.  This comment is a little shorter, but with the same apology - I didn't take pictures that show the brackets, which are now hidden.

The Pod is 75" wide and the Allen/Roth shelf is 72" wide.  I cut 1x3s two feet long, with 45° angle cuts at one end.  Then I attached 1.5" angle L brackets to the bottom of each 1x3.  The heads will contact the upper fabric of the valences.  One screw hole will be sticking up on each bracket at this point, and I attached the brackets through that.  Unfortunately, this is the photo I missed.


The next step was to install a runner (1" x 3/4") to keep the shelf from sliding side to side.  We also wanted to be able to pull the shelf away from the Pod's end wall as needed.  I set it in about 3/16" from each wall and added a screw through a faucet washer as a stop (below). 


So far, it's worked well although the medium walnut stain I used wasn't quite as good a match as I initially thought.  Also, I didn't want the shelf to fit real tight to the "track" but maybe a tiny bit closer would be better....