RH,
Thanks for the comments. I used .25 inch (approx 6.35mm) aluminum for the adapter plates. I did have to drill the forward hole in the frame for the top of each plate. You are correct, I also had to dremel the covers for the adapter plates but not for the boards themselves, see pic.
The boards have worked very well and are readily available since there are so many "wings" around. And you are able to relocate them wherever you see fit for passenger comfort.
Just give a shout if I can be of any help.
Regards, Lonnie