Can you reach the damaged area from behind the bed side? If so, deflate a beach ball, stuff the flattened ball behind the damaged area, and GENTLY inflate it to support the panel while you grind, lay up a cloth patch, and soak it with resin from the outside. Once it's well-cured, sand, shape, use a thin layer of filler if necessary, and prime and paint. Not an easy, or an inexpensive repair!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!