Rene, Nylon is lighter and/or stronger and is the first choice for lightweight shelters, quilts, clothing and packs. Basically, the two threads are identical except for nylon is stronger and polyester is less UV sensitive. Nylon can be manufactured in smaller thread sizes, though this is related to it’s strength and toughness. The typical 3.5% water absorption means a pound of nylon will absorb .035pounds of water at complete saturation or about .56oz. But, it was lighter than poly to begin with…close to 15% (or around 2.5oz/pound though some tests indicate closer to 30% in equivalent weights.) But, using the full material strengths means a more normal lightweight 3lb tent will actually weigh some 7.5oz more than the nylon one, less if using nylon-6 (similar to robic.)
UV resistance is unimportant since both suffer from UV damage. Nylon suffers more, but, was stronger to begin with at equivalent weights. But, mostly, we will be camping in shaded or partially shaded areas. My tarp is still functional after ~12 years of continuous use (~30 nights per year) for camping, though it has stretched and was rebuilt several years ago.
To me, it makes sense to use nylon thread for sewing onto nylon cloth. Normally, using poly thread, I have to use a looser stitch (about one click down) to maintain equivalencies in stretch between materials, especially on long stitches. Here, it doesn’t really matter. Both threads will work. But I agree that glueing alone could lead to failure. And it will likely be no stronger and heavier than simply sewing a daisy chain on. But again, I would consider the strength of the substrate material and use about a half to a one inch space at each end between loops with an “X” reinforcement to “grab” as much pack material as I could without creating score lines in the pack material. This will be heavier in the end, but a good permanent mounting point.
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