Don't know why that should be the case. My flat caps stay on at 150 kph (93 mph). Up to 130 kph or more even my leather Australian hat stays in place. Even though I am 6 ft tall it is all in my legs and sitting I probably seem about 4 inches shorter so it probably has something to do with the level of the head in the car.
What you are trying to say Peter, is that you manage to hold your hat on with your knees
I do use a baseball cap but more a sailing style one as they seem to stay on better. For LMC and the Shelsley vintage events, I wanted something a bit more period. Flat caps never really stay on my head until I found a leather baker boy style by Stetson and a linen version. They seem to do the biz!
