I want to fish rear view camera wires through the windshield surround. I expected a cross section of the surround at the top would look like this.

Windshield surround cross section.jpg

When I began drilling a small hole in the bottom, I hit aluminum. I thought I'd stop and check to see if anyone else had run wires through the surround successfully before I proceeded. If so, how much room is there in the sides and corners? Thanks!