I definitely wouldn't sew anything to the hammock body. What you could try is Velcro with industrial-strength adhesive backing. Put that on your hammock and then the other side onto the bottom of your pad. I doubt it'll hold up for long with folding/packing the hammock. I got a 25"-wide Thermarest ccf pad and so far, so good. It's so wide I'm not worrying about slipping off it. It holds the sides of the hammock out, too.
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