No matter what style bag/tote I make, I use canvas as my interfacing along with whatever batting I have on hand. This gives good shape but doesn't end up too stiff. I tried and wasn't totally happy with all the things other people recommended to me and it was serendipitous I stumbled upon canvas. When my husband and I decided to paint some floorcloths for Christmas gifts we had some good size smaller pieces leftover, so I tried them as interfacing and loved the result. Now I won't use anything else. I have several different weight canvas (some broadcloth, some duck and some heavier weight), and which one I use depends on the type of bag/tote I'm making.