Cracks propagating from the vent window tab are probably due to the upper mount for a breakaway mirror putting too much stress on the door skin.

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I bent this brace from a flat scrap about the same width as the factory tab so that it hooks behind the mirror nut plate and does NOT fully span the gap to the inner skin. That allows the tension to be adjusted by tightening the screws.

See the PREVious few pics...

Owner caption January 2013 · Photo 4879 of 5000