The original post found here. Original post's bag here. The bag I used here here.

While I was looking for the least expensive version of this bag, I came across a different version of the bag that seemed to work better towards this purpose. The big difference being that the top strap on the bag I used comes off and doesn't have any brass buckling. It has 4 loops (two on the top and bottom) on the back of the bag, which made super quick work with 4 zip ties.

Also, the leg buckle it came with added perfect as a seat strap. Loving the look of having both of them on there.