On second thought, it looks like you have some room on the backside to play with. If you could reduce the lip on the front side of the adapter so that the speaker is not pushed so far towards the grill, there might be a chance for this to work but there's still that issue of how to secure it.
Bottom line is, you got a lot of trial and error on your hands. I went through about 5 or 6 versions of the adapters I made before I came up with one that would work for "most" applications. BTW, that magnet is pretty big which could be another problem. Have you actually tried to test fit this into a car yet? The diameter of that magnet could be a problem.
09 E90 M3 - Interlagos Blue / Black Novillo / Sycamore Anthracite / Eibach / HRE