I have done this one,too. I cut out four of them and did them at the same time. Glad I did them that way because I am not sure I would have done the rest if I had done one at a time. Everyone loves them.
Pattypurple, how did you use soft and stable? Since you don't iron it on, did you quilt it to each section?
I cut the Soft and Stable the same size as the outside pieces, basted to the fabric and then stitched as directed. The needle sews through the S&S just like a hot knife thru butter. The weight of the total bag was greatly decreased and the bag stood up really well. The one I made with the suggested batting and interfacing many years ago has collapsed on itself and looks very limp.
Just had another one requested today so looks like I'll be back in the sewing room.