They've worked better than I expected, happy kids and a nice comfy sleeping space for everyone. Using them again twice this month for trips to Eastern and Northern Idaho. Some quick bullet points:
-I used tubular webbing from REI for the attachment points in the van, 4x each front and rear around supports. 3' sections (~$1 each) with a water knot have worked great and are tucked back behind the wall panels when not in use.
-Rope is static line, also from REI. IIRC these are 10' sections (~$3 each), figure 8 follow through knots on each end to attach the carabiners.
-Carabiners are pretty cheap Walmart items with 150 lb limits. 600 lbs total per hammock is a safety factor of like 8-10, so I'm not worried.
-Canvas is cut from a drop cloth I got on Amazon (
link), it easily did 2 hammocks, even after shrinking during a wash cycle.
-I used leftover canvas to make hanging pockets on each hammock which have been very useful to store stuff sacks, shoes, water bottles, etc.
-Upholstery thread and denim needles got the sewing done. I broke 2 needles, both my fault. Easy peasy once I got the hang of it.
All in I think I'm at about $60/each, you could definitely do it for less. I went overkill on the hardware, most of which isn't necessary. PVC Tees are the expensive bits, $3 and change each. Everything else is small potatoes.
