Metric HW--socket vs. cap screw question, and a dealer story

[Jonathan Monetti]

In the process of replacing most of the important hardware on my Coupe,
mainly suspension.

Question:

I have access to a large collection of (free) 12.9, black oxide hardware,
90% of it socket head.  Wondering about replacing some of the stock 10.9
suspension bolts with these.   Since the head is obviously smaller, I am
concerned that the increase tensile strength will be offset by the
concentrated load on the smaller flange.  Any BTDT's, or engineering
expertise out there?   (Did I mention they're free?)



Story:

Scary dealer visit.  Needed some missing fasteners for my A4's bumper
valance.  At four dollars per, I almost wet myself.

Undeterred, I also asked about hardware for the Coupe.  Conversation went
like this:

"Do you have four of these (plink) and four of those (plunk)?"
"Maybe.  What kind of car are they for?"
"A 1987 Coupe GT"
"What kind of car?"
"Coupe GT"
"And who makes that?"
"Ummm...Audi."
~Silence~
"It's like the 4000, only with two doors.  Looks like a big Scirocco?"
"Ummmmmmm..."
"Never mind."

I can't blame it on youth, the guy had ten years on me.  To top it
off--nothing in stock.  Has the hardware really changed that much??

Jonathan Monetti
2002 A4 1.8tq (pos)
1987.5 CGT