Did you do your whole roof or just strips? I've read various ways to do it like putting on a strip at a time and knocking on the panel until you're satisfied with the sound. I haven't had my headliner out for the better part of 10 years, so I can't recall exactly what it looked like for reinforcement under there you might have to work around. I'm pretty sure I at least coated it in POR-15 though, so hopefully it's still steel and not rust...