Fathers day gift for my old man was a new backpack so I just got pic related since he doesn't need it anymore. I really like the sizing and simplicity of it, its 45ish L just a main compartment up top and another below for my sleeping bag. Its an REI bag and from the look of it it's from the 90's but I can't for the life of me find any info on it other than that. Could someone give me a hand on how I should be fitting this thing? My last bag was a 32L day pack that I would always end up way overfilling and would never really fit 100% comfortably so any advice would be appreciated.