SilverlightPony, I appreciate the time you took to explain.
This is how the OEM brackets on the gt86 look like:
it's not only shorter, but the mounting holes are also located differently than what you have. to complicate things, it has four of those annoying little bumps, as opposed to only apparently two on the fr-s.
I'm still trying to figure out how to get rid of those 4 bumps, NONE of them match any of the holes on the ca-fi when I allign the brackets in the correct position. To make things worse, I'm also travelling for a couple of weeks, so I have a limited set of tools. The only things I can try are either a metal file, or a serious hammer.
From the looks of it, the mounting position in the picture is wrong, anyway. I think the brackets should sit about 1 cm towards the back of the unit, from where they are right now. However, the bumps will still not fit any of the holes on the side of the ca-fi.