My goal was to mount both the plate and the light under my seat. However, the seat is super low and it doesn't leave me a lot of room. I knew the plate mount would have to be shallow, but I figured it would still be somewhat visible.
I started by making a nice cardboard cutout using an Eggo waffle box.
I then transfered that over to a piece of 1/8" aluminum and added the brake with my vice and some clamps.
I was super happy with how it turned out. However, as I suspected, I couldn't put much of a brake in the part. It was getting too close to the tire. I thought I could get away with it as you see it in the pictures, but when I put the seat back on and sat on the bike, I could tell it was going to be too close no matter what I did. Damn. I really wanted to mount the license plate here. It would have been clean, sleak, and out of the way.
From there I moved on to plan B. I modified the piece of aluminum to make it fit the lower shock bolt. I really didn't want to go with a vertical plate, but I didn't see another way around it. Oh well...I don't think it looks too bad for a compromise. I checked the fit after I finished it up and with my feet on the pedals everything clears just fine.