The important difference between men’s and women’s packs is the shape of the shoulder straps. Men’s are a J shape and women’s are an S shape, which reflects differences in chest shape and size. In my experience, this difference is not as essential as torso length (not even in the ballpark), so if the opposite gender pack is a better fit, then that’s the pack for you. Some gear manufacturers (such as REI Co-op) are beginning to move away from gendered colors on packs, as well, making this an increasingly viable option for people trying to dial in their pack size. Very petite women can also look at kids’ backpacks modeled on adult versions for a better fit.