Good advice, Derek, though you've dampened my euphoria. This car hasn't seen any water, other than an occasional washing, since I bought it. And the P/O, who was quite fussy, told me he'd never had it in the rain following its restoration in 1991. Always garaged since then, too. Additionally, the car was undercoated from new and the undercoating on that member is completely intact. The bolts snugged very tightly using a 1/2" drive, so I'm hoping that it was simply a matter of their working themselves every-so-slightly-loose over the years. However, I'll keep an eye on it regularly in case it's rusting from the inside.