I think the best protection is something like this, doesnt need to be carbon.
Velcro it on, so if you do take a big hit you can remove it to inspect for any damage underneath.
A friend has one and has taken several hits when he has catapulted his 100kg when hitting fish. His last big one broke the boom clamp and mast but the board and protector was ok.
I've used Gorilla glue for sticking a Unifiber pad down, as the board under the pad wasnt completely flat.