Anybody fill the area between the trunk / fenders?

The quarters are cut to the body line under the marker lights, patch panels (Goodmark, AMD won't make 'em) trimmed to fit. Trunk extension cleaned up as best as can be for a car that has had the wheel opening enlarged at the rear. The Goodmark patch panels seem thicker than the OEM metal BTW. Gonna lap seam them in on the backside and will grind and seam seal.

He just threw out the idea and I was gonna see if anyone had tried it. Not the cheap insulating foam, the part A / Part B foam, but the high dollah auto body stuff. I at first didn't like the idea cause I have seen too many cars that filled the area with whatever and bobdo'd the outside smooth and shot the paint.

The stuff we found in there... Drill bit, wing nuts, lotsa dirt and grime. No wonder they rust out.