I've not had to deal with this, because my Speedy is always stuffed, however, I've been reading about what a lot of people use to stiffen up the bottoms of their bags. I've sewn a number of purses and the best and lightest base material I have used is found in the quilting section of the fabric store. It is called "heavy duty template plastic." It is sold in a sheet and can be cut with scissors, is super-light and holds up the bottom of bags very, very well. You can even sew a fabric sleeve to wrap around it, or leave it like it is. Don't know if this would help anyone, but never read anywhere about people using this material.