It would depend on your friend's sewing machine but it would need to be a very heavy duty machine. It may be better to take it to a sailmaker. I took a tramp to a local tent maker here in Japan to resew around where the sun had destroyed the thread. They make large awning type tents out of similar material as the vinyl tramps here. A budget option would be to get an awl and hand sew it on, it would take a while but as you only need to sew the hiking straps in a few places wouldn't be too bad. Something like this one from Sailrite.
https://www.sailrite.com/Speedy-Stitcher-Sewing-Awl-KitAs for hiking strap material towing straps are cheap and nice and soft or maybe some old seat belt material from a scrapyard would work but a bit harder on the legs.
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Hobie Wave 2004
Hobie 14 1991 Plum 40525
Hobie 16 1985 Nationals White Prism 91964
Hobie 16 1985 European Championships Palma 114072
