Hmm, started working it out: seam width approx 10mm, approx length 1500mm, four seams = 60,000 mm2 = 93 square inches. Roughly With the distance between the front seam and the rear seam, in terms of air resistance, I think you can consider both as frontal area combined. But it only works out to be 0.64 square feet. So we're both wrong but I think everyone agrees it was a worthwhile exercise