Glued and sewed a larger piece of gear repair tape to add fidelity to the ripped edge: Then sewed the rip itself with fishing line (the strongest thing I could think of to hold the weight of the bag's contents, plus I just happened to have it at home:

As of this post, I've been using it for a week, and it's held up pretty well. I may add some sealant later to hold things in place.

Now all that's left to do is replace a missing zipper pull and fix some rodent damage to the front compartment... I may post about that at a later time