My 75 buick lesabre convertible came with a matching fiberglass parade boot cover. My question is it just like the regular soft cover boot and by that i mean i can keep the hard boot on and drive around and on the freeways with no worries about it coming off?
I drove around town with my hard boot on my '74 with no problem. I didn't drive it at highway speeds with it on, so I can't speak to that. The two Dzus fasteners are all that hold it down on the front. On one hand, I don't want to trust them at high speed. But on the other hand, each of my saddlebags on my Harley is only held on with two of those, and I've loaded them down with gear and traveled many miles with no issues.
I have traveled all over the country interstate driving in 2 72 Centurion convertible with the "Customline" fiberglass covers with zero issues or problems and I travel with top down always unless it's raining. I have a heavy foot so they saw high speed interstate driving. The way the airflow is with the top down it does not lift the front of the cover. You could run with the front fasteners undone and it's won't lift.
The only problem might be "dirty air" from passing or being passed resulting in a lift vector. Once a "piece" of dirty air and boot touch and "get busy", you will recall all the French words you thought you forgot. "I am a leaf on the wind; watch how I soar" -Wash
x3 - I've never had a problem with mine, and the leading edge velcro strips are pretty weak. That said, anything you can do to shore them up cant hurt. Those things are expensive.