Re: bimini up or down
three issues:
can your bimini survive the winds open? Most likely, yes, it will last longer than you will. They handle* 50 mph but your boat won't.
Are you concerned about performance? driving with the bimini up is like dragging an anchor. But that is just a trade-off. My wife and I run to the fishing grounds with it folded, open it and leave it open even if moving a mile or so, and fold it up for the run home. The wind compensates for the lack of shade.
Could it affect your safety? If you are caught in a gale your concern is to get to safety quickly. A bad gust on top of dangerous winds could catch your bimini and screw up your control of the boat, or break it loose and injure/distract you and the passengers.
*although it would add to the wear and tear, so it's not a good idea to do it regularly, or trailer it open.