Sounds to me like you might be trying to screw them!
In my past experience you can only claim for stolen boards and then only if the boards are listed and detailed on your policy.
How can you logically claim for damage that you may have caused? I would guess that if your boards are listed and covered for damage then you maybe able to claim for that damage.
If you look in past SUP posts you will find lots of comments on tying down your SUP.
DJ in particular makes several references to this.
Just my thoughts.
ET.