I'm all for make it yourself gig bags.
I'm planning to make one out of an old pair of jeans/denim
for my Backpacker ukulele (Soprano). It will probably be just a drawstring gigbag. I'm not sure
if I will try to make a backpack out of it. I just want it to fit into a larger, drawstring backpack,
which will have my music stand, a 3-ring binder of songs, a cushion for sitting on hard surfaces,
a fan, bottle of water, radio, etc. It's my Waikiki Backpack for when I'm wandering the sidewalks
on vacation.
Keep uke'in',