glh carl,
there is a big difference between a skin and a plank,any electra engineer knows that the wing is not of the usual airliner constuction,these planks have had a corrosion problem. Because the planks are much thicker than your average wing skin they have a much greater stuctural load,the corresponding spars & stringers are lighter,an engineering trade off,whilst it is not economical or practical to reskin an airliner wing,many electras have had their wings replanked.