iFixit should really clarify whether the film covering each of the battery packs should or should not be removed. Based on dpchoung’s comment I removed this film. It was not obvious or easy to remove and as I was doing it I realized that maybe this was not a good idea as I was concerned the packs might be damaged in the removal process. I suspect most people don’t bother with this film. Later, clicking on the forum exchange I see conflicting advice. My guess is that the film provides added protection and has minimal impact on thermal issues. I am sorry I went through the bother of removing the film and hope no damage was done.