[tucsonjwt]

Thanks.
I cut down a piece of 2 x 6 on a radius to match the curved metal in the cab corner on top (traced out curve on 2x, then cut along mark with sabre saw) for top "bracket". Cut a piece of paper to match the floor of the cab corner and accomodate the cross brace in the far corner - trace the cut piece of paper on another piece of 2 x 6 and cut that with a sabre saw to make the bottom bracket. Dado a 3/8" x 3/8" rabbet in the lower inside edge of top bracket, and the upper inside edge of lower bracket - now you have a "pocket" for the speaker panel to rest in.
Drill pilot holes and angle screw the top and bottom bracket with 2 self-piercing screws each to the curved metal on the top, and the metal cross brace on the bottom.
Once the brackets are installed, use a piece of cardboard to fit into the opening between the brackets to properly size the speaker panel. Trace the cardboard template on a piece of 1/4" hardboard - check fit. Use the speaker template to mark the speaker in the desired location - cut speaker hole with sabre saw. Used 3 self-piercing screws 1" long (top and bottom) to
mount the speaker panel (after attaching the speakers/trim/grills to the panel. Attach the speaker wires and screw panel into place.
The problem is our trucks are apparently not consistent dimensionally from one side of the truck to the other, or from top to bottom in the cab corners, so it is a lot of trial and error. I like it better than a piece of open sheet metal hanging from the cab corner, and cost $0 with scraps and paint I had laying around the shed. I spent about $25 for the 4" JVC speakers on the net - P.O. already ran wire for speakers, which I found when getting ready for new carpet. With 4" speakers, there is still room left under the speaker behind the speaker panel for a secret hiding place or small door to store small items.