Well, we have tried our faux packraft against our Alpacka raft on a four hour Grade 2+ section of the Wonnangatta River on an overnight trip (during which we saw 9 deer!) and apart from some slight abrasion to the lamination of the poly tarp (nappy) the $40 raft stood up splendidly. I found a 33 millimetre metric coarse nut which I was able to cut thread with to extend and create a double paddle which also worked well. The Gaffer tape held up, but I think tarp clips would work better. I can definitely recommend this expedient as an intro to packrafting.
See Also:
https://www.theultralighthiker.com/2011/12/03/home-made-pack-raft/
