You did a good job and took good pics! I did pretty much the same thing, even have the same basic shape plate only I used 1/4" and bolted directly to the frame. I just never saw myself ever taking off the bags and carrying them around. Liners are a lot less cumbersome.I used Easy brackets and a pice of 3/16" alunminum plate. If you search my picks you can see how I did it.
Hey Klattu,Here is a set I made a few years ago...photos and tips...
Notice the 'C' pipes...I wanted to mount them as low as possible