Are you kidding me? You don't need curved needles. The liner partially comes out. Its only attached to the flap and the edges, so you un-velco it and get your hand in there between the liner and the flab. You hand should be inside the back and the threaded needle should be in that hand. Now poke outward and BAM, you can now start sewing without puncturing your liner or using curved needles.
Downside: you will stab your hand that is inside the bag a bunch and the needle may not always pop out where you need it too. These aren't huge downside, but definatly a lot easier than using a curved needle and the seem grip, which may be useful for other bags.
I would post how to pics, but my bag is a thousand miles away right now.