Boy that looks a lot deeper than wide, so is your approximation of 8x9 close? Looks more like it would be about 12 deep if it's 8 wide, or 15 deep if it's 9 wide. Only reason I bring it up, in my use deep narrow bags tend to shift whatever I need right to the bottom of the bag and require a buncha digging.
All that aside, I really like the looks and construction. Great idea.