The "torx" stainless screws from Microfasteners are 100 degree, so work fine with aviation tinnerman washers. I have them on my wingtips, vertical stab fairing, and wheel pants. I don't have them anywhere on aluminum.
New Smyrna Beach, FL
VAF Paid 1/10/2018
"In '69 I was 21, and I called the road my own"