I finally started cutting out the exterior pieces from the shower curtain. Now that I can hold the fabric without the weight of any seams, it seems a little thin to me now and I wonder if I should interface it. Honestly, it feels a tiny bit heavier than the drop cloth I used for the practice backpack, so I'll probably be okay without interfacing, but will have less body/stiffness to it. The pattern calls for foam interfacing on all the exterior pieces, and I'm still deciding if I want to do that or not.

I linked the four build videos that go along with this backpack. I have to say I don't condone cutting around pattern pieces with a rotary cutter like Jen does, and especially so close to your other hand. How do I know? Shaved a bit off the side of my pinky a few years back. Rotary cutters are insanely sharp!