Kick panel help...

[SunSoaked]

Didn't get any response in the audio section, so I'm expanding my search. I'm wanting to install some 6 1/2" speakers in the kick panels. They look like they will mount flush and not interfere with the e-brake on the d/s. However, the big question is; What's behind the panel? I'm worried about structural braces that run adjacent to the panel or other unexpected stuff.
Has anyone ever done this or seen what's in there? Anybody have access to a junk cab tohat would be willing to explore for the sake of adding to the public knowledge base? I'm not concerned about the water issue if in fact water can get into that area cause I'll be using sealed baffles. And please don't suggest I cut holes in the doors, that's not an option.