youve got the perfect material there - ive just made my cover out of similar. forget stitching it, weld it. ive done mine using a heat gun and a wallpaper seam roller. as for shaping it its pretty simple, get the material to sit flat as possible then gather up slack in various places, cut at these points and allow the two 'flaps' to overlap each other and mark up the points where the overlaps lie - remove from boat, line up the flaps again and weld. take your time and think about how you want each part to sit around your boat. its essential that you clean with solvent cleaner before welding as it just wont stick otherwise!
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