1970 Charger: What is the purpose of the suitcase under the Dutchman panel?

[ACUDANUT]

I'm sure it supports the front edge of the trunk opening.  It's bigger than any other Dodge, and completely flat, offering zero strength on it's own.

I think that you figured it out.
Anyone that knows sheet metal also knows that a flat panel is not as rigid as a curved or one with some ridges, indentations or creases. The flat Dutchman spans between the C pillars and in that area, the trunk lid and springs are attached. This "suitcase" isn't an elegant solution but maybe the function was just to provide strength in an area that would otherwise shake and buckle without such a robust support.

Kern Gog, I think you answered your own Question. 
BTW I pm'd you awhile back. Got ghosted.

[Kern Dog]

You sent dick, pictures, man...

[ACUDANUT]

Whaat  ?    I sent you a pic of Vietnam era jeep with a rebel flag on it. 

[70 sublime]

Still not sure what the suitcase is for
I have a 68 Coronet parts car laying around so I went to see what it was like
The front edge of the trunk lid is a lot wider than a Charger but it has nothing fancy going on at all
The only thing it has were two C channel type braces coming from edge of glass to the edge of trunk opening on the under side of the Dutchman

Maybe because the Charger roof comes back so far it needs more support ??

[Mopar Nut]

It's there so the Duke boys can hide their moonshine. 

[Kern Dog]

Still not sure what the suitcase is for
I have a 68 Coronet parts car laying around so I went to see what it was like
The front edge of the trunk lid is a lot wider than a Charger but it has nothing fancy going on at all
The only thing it has were two C channel type braces coming from edge of glass to the edge of trunk opening on the under side of the Dutchman

Maybe because the Charger roof comes back so far it needs more support ??

I don't know the Coronet panel very well. Isn't the Dutchman curved? If so, it is inherently stronger because of that.

[Ghoste]

It's there so the Duke boys can hide their moonshine. 

They didn't do a very good job then, because they got caught which forced Uncle Jesse to make a deal with federal government of the US of A to keep them out of the hoosegow.