[BobbyK]

Double walled tops have no metal support brackets like the single walled tops do.
That's why they sag.
I suppose GM thought the inner layer combined with the outer layer would be enough...I have not heard of a fix for the double walled tops.

I think the only remedy would be to somehow mold in some type of support bracket...you'd need to know how to work with fiberglass though.

Here is a scan of the bracket molded into the single walled top.Also shows the layers of the double walled top.


Double walled top.
















Single walled top bracing.









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