Back in the dark ages when we actually did metal working instead of replacing whole panels, dents in double wall areas like that were often worked with a "pick tool"- - - -a spring steel rod with a bend in it that was inserted through a hole drilled in the interior panel. A dent would be gently ironed out by using the tool as a lever. I've seen those tools offered on Ebay on occasion.

www.ebay.com/itm/286111920154?

www.ebay.com/itm/196553021349?

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!