So, some photos.
The flat dimensions are 25" across the top, 16" top to bottom, and 16" across at the narrowest part of the base.
This is the inside of the bag.
Front flap stash/pie/pump pocket. Here you can see one of my two beefs with this bag; the Freight patch (and it is a great logo) was sewn on last, and is sewn through the front flap and the pocket, effectively sealing off a quarter of the pocket's length. If I really cared that much, I would just take the patch off, solving the problem.
The interior document pocket is huge. It stretches the entire length of the front panel of the bag.
My favorite thing about the Freight is the way the shoudler strap is attached. Rather than being sewn on to the side of the bag, it is sewn onto the back, facing away. When you're wearing it, this means that the strap has a natural tendency to wrap the bag around you, while keeping the corners from poking into your back or shoulders.
My other beef with the bag was that the waist strap it came with was too short to be useful. I am a small guy (5'9", 135lbs) and I could only get the strap around my waist when the bag was completely empty. It took about 10 minutes to sew a longer strap and an extra little buckle on, but it was still a pain in the ass. I'm used to a stabilizer strap, so I attached it back on that way rather than as a waist strap. I'm sure he could make it either way for you.
Insanely beefy closures.
The adjustment buckle is simple to use and can be lengthened or shortened easily with one hand.
When stuffed to the max with pillows, there is still a lot of extra strap left over. The straps are attached to the flap, rather than the base of the bag, so they can be easily tucked inside the bag if they're not being used.
While I can't really say what the 6-Pack CapacityŠ (6PC) is, I would put the Adorable Kitten CapacityŠ (AKC) at around 10. Maybe more, maybe less... they get squirmy if you try and pack them too tight.
Anyway, I hope this helps.
EDIT: I forgot to mention that this is a size medium.