Rear Speaker Removal Mazda 929

I want to replace the rear speakers but i cant figure out how to get the grills off in the rear deck behind the back seat  of a 1991 Mazda 929.

Also wold it be a good idea to install ports up there aswell since there is a big metal crossmember wall behind the backseat.   Installing Ports wouldnt weaken the cars body structure would it? even if theres a main crossmember behind the seat..

Robb

no taking grille covers out without breaking them...gotta take out the bottom of the back seat then the back of the back seat...some plastic fasteners on the rear deck...the 3rd brake light...then the rear deck...as for the ports through the rear deck...unless you know about boxes...tuning frequencies...and mathamatics i don't reccommend it...just slapping any old size port in there is not only gonna sound bad...but will end up making you and you car look bad...on the other hand...if you have built a custom ported box before and successfully tuned it to a certain frequency then yes you can do it and get it to sound good...if not...leave it how it is or you might make it sound worse