I really, really, really think that's a bad place for a backstay.
No history of problems with that backstay. It's set into a massive hung
of glass and is bulletproof.
And....
http://www.floridaboats.net/images/3.../slides/5.html
No rust stains though I've seen such stains on premium boats with
so-called SS hardware.
RB
35s5
NY