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You did access this site didn't you?  http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/73_StepbyStep/73_Step_by_Step.html

It shows how three rows of stringers would have been rivited in place to stiffen the cover.  Without these batten/stringers of sorts, a patch riveted around the periphery to the fuselage alone would just blow out under elevated air pressure. 

I think the explanation the researchers at TIGHAR did in this regard is the best explaination for the three rows of holes more or less centered off of the two top and bottom fuselage rivet joints. 

Sadly, the rivet holes for the fore and aft joints are missing.  But owe that one up to entropy and just deterioration over time. 

As for the contemporary photos of Electra, owe not being able to discern them up to the quality of silver based development of pictures.  HavingDigital technology is a great thing, but the pixelations in old photos can not be enhanced even if enlarged, only a processed negative can offer greater detail.  A silver oxide print is only a good as the process used to print it.  And sadly in smaller photos details suffer and are often lost.