I have 5.25 inch JBLs in the front. It required enlarging the door (metal) pocket a little to fit the magnet, but not much. I took the door panel off and used a dremel. Easy job. The JBL are quite deep, and seemed that it would require a spacer, which I didn't want, so i modified the cover a little and drove securing screws through the cover (now you can see it) rather that using the JBL snap on spacer for the cover. I also had to cut larger opening in the door panel, which was an easy job with a sharp knife. It works Great!
In the back I have 6X9, but as mentioned here by someone it was quite a job. I had it done by my garage boys that spent half a day working and manufacturing custom new brackets.
BTW, I also used 22lb of RAAMmat BXT II from RAAMaudio - Automotive sound deadening products, on front and rear doors, some on very front of the foot well, and rear wheel wells. My Disco is now quiet as luxury car, even my wife noticed. Awesome sound and you can have a normal conversation at 110km/hr on the highway.
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