I have driven my '56 with factory style visor for many miles at 75 mph and more and it hasn't been ripped off yet. With all the noise an old truck makes at 70, I don't see how you could determine how much of it is made by the wind on the visor.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.