It's easy to get tested pack fabrics online. This would be my preference over using untested "brand X" stuff that was developed for other purposes. Go to Quest Outfitters, Seattle Fabric, Rainshed or Through-Hiker for materials and plans that have been "trail-tested". They all have websites. You can get a kit to make a G-4 pack from Quest and a kit for a Ray-Way pack from Ray Jardine (also on line) and have all you need to make a good light pack for less than $100.
May I walk in beauty.