I've decided to dive in and follow this method in making a Backpack for my Fiance's Pred build.
Obviously this is in the very early stages. I bought the electrical conduit as VinMan directed, and used that as a basis for scale for everything else.
I eyeballed his template for the "scales" that go on top of the conduit, drafted it out and cut out three of them and glued them on. Then I started on the base of the backpack. VinMan appeared to have made his out of several layers of Sintra with a balsawood top. I used EVA foam mats instead to save on weight, and topped with one layer of Sintra with the designs cut out.
Then I fashioned a "bracket" to hold each end of the conduit above the base. That's as far as I've come so far... I'll be working on the sidewalls tonight, and then moving on to the surface details.