I have a 1977 starcraft. I just acquired. The center of the deck is soft. I weight in at 275lbs and can walk on it, but I feel a soft spot. If I should replace what do I use? The floor is covered with a rug of sort. Is it simple enough where I just pull the floor and replace with a piece of plywood? Or is their more to it then just that? It has been in the weather for a few years uncover.