Looks great!!
How long did it take and what material was used for inside and outside looks good.
It looks like a stucco type of material.
Im sanding a 17 " down and not sure what to use.
Thanks good job,help me with what you did.

As an outside observer, my guess is he used the same material used to line truck beds on the interior. I have talked to a lot of boat painters who recommend it for its plyability, durability, and sound deadening qualities.