As you should know I used to own 12 or 13 Gis all different makes, and my OTM Medieval Gi has heavy (thick) Duck Canvas pants, and in only a short while formed a hole that I fixed. Duck Canvas is actually what they use for standard linens like, bed sheets, curtains, clothing, etc. Ripstop is used in place of using a heavy material, but able to keep the same durability as heavy materials. My ripstop pants from Redstar, Atama, Zombie, Black Eagle, etc, have all been solid, only burning through actual stitching and not the material. Cotton twill (same as denim) seems to be the toughest cotton non-ripstop material in my experience.