I just picked up SO MUCH 50mm webbing!
I did some measuring and calculating and it looks like I'll be able to get away without any backing fabric at all, just a pair of vertical 50mm strap lengths for each half of the bag frame. I'm thinking I'll use hook & loop to secure it under tension but I picked up a pair of side release buckles anyhow to cover all my bases.
And I *think* I have a functional three-buckle quick-release design for securing the frame to the bag... 🤞