I have an Seek Outside pack made with X21 and it’s done 4 weeks in Alaska (2 2-week trips) with LOTS of brush, and a one week trip in WRR. The only damage came from the WRR trip where I was traversing car size talus and had to scoot across a few pieces. I had a Bearikade which has rather sharp corners, and that along with the granite created a few small holes.
I have found X21 to still be more durable than 150d polyester hbrid cuben.
The perfect fabric might be an X pack with only the Nylon face (perhaps the 330d if they made it in a non camo color) and .5mil PET layer with no X grid or interior scrim layer. I think it would be light and durable, not to mention permanently waterproof.
