Replaced my rotted out floor pans with new 16 gauge pans from CCOT. They came with what appears to be a heavy coat of gray primer. We're repainting the entire inner tub, but I'm not sure what to do on the underside. I'm in Texas so no rustbelt or road salt concerns. The body shop guy said he'd recommend just applying undercoating directly over the primer. Does that sound reasonable? Seems like they should be painted first.