That to bad, my 6.5 dropped right into the factory holders once I gutted out the stock speaker.
I just took out the speaker part and it mounted right on the raised ring:
Even fit on backwards, then we realized it was screwed into the wrong side:
Sorry it doesn't work with yours.
My stereo thread:
http://www.subaru-svx.net/forum/showthread.php?t=54516