Maybe his 6x9's are mounted on spacers which locate them close to the rear window almost touching.
I had to remove my 7x10's for rear window tinting as mine pretty much touched the rear window.
Dude,now that you got the speakers out,just throw the backseat back in if your worried(i would be)
On a r32 its just 2 or 3 clips and 2 bolts.
EDIT: spacers,i knew it!