Originally Posted by cth350

The side walls where the rear roof pillar meets the rear quarters is no less than 5 layers of steel welded together. It's easy to slice apart using a sawzall.

In your case, I'd do what the racing folks do, start by perforating the wall in a honeycomb fashion. Remove the metal in the flats. Don't damage the ribs. You need to do it with a chassis punch. Presuming of course, that you want the job to look good. There are some engineering guidelines for size and location of the holes. It's a question for a mechanical engineer. Also, you can weld a series of stiffeners to what's left.

You get extra credit for keeping the job as "original" as possible. In this case, that means factory parts. You'll find that correct benz firewall material is about 60$ for a piece large enough for one car. You might want to use it on what's left of that back panel to cut down vibration. Then again, its sound deadening quality may be exactly what you don't want.

-CTH