NO need to cut up the car at all. I have 2 pioneer 300 watt subs. More bass than I need. 2 original tweeters in front by the mirrors, 2 below (by the hood latch area) and two rear on the deck and two subs as shown. Do it like your proud of it or don’t do it all. I attached a pic but not sure if I did it right :)

86 535i 215000 klms
1961 Volvo Pv 544

I understand your dilemma. I have the same one! I just got HUGE 5 1/4" component speakers for all 4 corners and a nice amp for Christmas. To fit 5 1/4" speakers up front requires lots of hammering, cutting, and rust-proofing!

The rear deck and metal trunkwall are solid. To get ANY sound through them, you must cut them open. I am no sound engineer, so I have no idea what to do from there. But I do know that the rear sheetmetal hinders the sound drastically. Also, cutting large openings cuts down on the structural integrity severely, so it's good that you will be reinforcing the area. Have you seen Ed Teller's website? He's a really cool guy. He lives about 3 miles from my parents, and I've met him in person. His 535is used to have an M5 engine until he blew it up (timing chain went at the dragstrip). He knows stereos and sound, so I will be asking him about his setup in the near future.

He cut out the rear sheetmetal because his trunk locked and a poorly placed bungee cord kept it locked no matter what he tried. SO he cut out the rear metal to get the bungee cord off. Then he noticed a big difference in the handling. Barry and I from bimmerworld did the same thing on his M3 years ago, and we noticed the car handled like crap the next day at the autocrosss. So Ed had bimmerworld fab up that brace and weld it in. He said it's better than new. Barry and I started our road to cage fabrication on his M3 once we realized what we cut out was actually structural.

Check out bimmerworld and Ed Teller's website on E28s.

JamesM