the first thing I did with both my red and grey is set them in the sun flat for a few hours...(I'm in florida so we still have pretty good temp)..I'll bet you could get a better "flatness" with laying it on glass or counter and a hair dryer used on low....
the poly folds are strong so it lasts and eventually it flattens with use - here is a ipd3 cover that has been used for 18 months daily for travel and presentations - it's flat (on a incipio back)
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Feather back?