When you don't know where your board is, getting your hands up on your head like you are on the ground curled up and taking a beating, (for lack of a better way of describing it) is good policy IMHO. You're blind, and it isn't perfect, (you can still be hurt) but it cuts down on the angles of attack. It's worth a go.
And I've felt/seen some hideously sharp fins. I really don't think you are going to lose much performance if you take a piece of 80 grit and slightly dull the trailing edges. Again, not perfect, but worth a go IMO. If you are riding a quad it's like having four knives on attached to the back of your board. You pull into a closeout tube and the words frog in a blender come to mind. There are different opinions about how to set up a fall in that situation. "Stay on and get blasted off" creeps me out. Some say flop off the tail. That can work in big stuff where you have more time I suppose. Less chance of getting sucked over. Makes me feel like I am offering my twig and berries up to my fin cluster. In tight tubes on a small board, going off forward and intentionally stuffing the nose (pearling) so in theory, the board goes the opposite way you are taking your body. I don't know. Try something. Stay aware and stay safe. I'm going surfing...