Comments on some of the negative views regarding Osprey rucksacks:
HIP SUPPORT - the pack - any pack from any manufacturer that has a padded hip belt, that belt must ride on top of the Iliac Loop of your hips. Ladies you know what this is. Gentlemen, this is the big "loop" bone of your hips - the widest part (look at a skeleton). It is located just BELOW the normal belt line - assuming you do not wear your trousers around your hips.
The weight is borne on this bone - one of the strongest in most people after the femur (big leg bone). The padded hip belt, and much of the pack weight are carried here - NOT on your shoulders and back. It makes a BIG difference - trust me on this. Last Spring I wandered the
Camino Frances offering to help adjust people's packs so they better fit their frames. No one ever complained, and several offered their thanks, repeatedly, over a period of weeks...just part of the "helpful hobo" service.
That is why women frequently sit their toddler-sized children on a hip when they try to do something with their free hand. On the other hand, if you do not have a significant "shelf" there aka "no hips" you do have a dilemma. I inherited my mother's family's Sicilian body frame. So I have plenty of hip to spare...
BACK SUPPORT - The Osprey Kestrel series has a mesh ventilated air suspension system. The pack never touches your back. The mesh panel does. The outer back panel also has a ventilated, horizontally-aligned, flow-through accordion frame to allow cross ventilation from left to right and vice versa.
You need to adjust the torso length of your rucksack and the shoulder strap cinching straps to do this vertical alignment properly. The Osprey, as do many other well known hiking rucksack brands, excel at minute (tiny) adjustment. Their packs generally have adjustable back panels using the mother of all Velcro pads to permit centimeter or fractional-inch adjustment up and down making the torso length taller or shorter. The upper and lower shoulder adjustment / cinching straps then permit you to pull the load higher to your shoulders and closer in to your shoulder. You should choose a pack with both upper and lower adjustment straps.
In my case, I started with my Medium / Tall Kestrel 48 adjusted to the third "bird silhouette" mark on the Velcro pad. By the time I hobbled from St. Jean PdP into Burgos I had to shorten the back panel and torso length to the smallest possible adjustment. Fortunately, my pack rode perfectly afterwards. I am 5 feet 11 inches (180 cm) with a "stocky" frame, large barrel chest with a short torso - BIG boned. So, for a troll like me, the Osprey Kestrel series offered the perfect blend of form, function and most importantly the ability to be micro-adjusted to my individual needs.
With torso / hip and shoulder / back adjustment done correctly, and I speak from experience, after a couple of weeks, the Osprey Kestrel rucksack felt like a comfortable old shoe. It just fit and fit very well. In fact, when my Camino was all over with, I actually missed "saddling up" in the morning. It actually felt good to have the pack riding on my back. I felt less dressed without it.
All this, and my previous comments stated, together with the other very good observations in this thread, if I were buying another pack for my upcoming May 2014 Camino I would consider the Kestrel 38. However, and this is fully described in one of my earlier posts on this conversation, the Osprey Kestrel 38 and 48 liter rucksacks are the same height, and likely the back panel has the same range of adjustment because of this same vertical height feature. The volume difference is made up by the 38 liter pack being slightly narrower and shallower. (Read my earlier posts above)
This established, if I TRULY wanted the optimum solution of perfect torso adjustment and capacity (48 liters +/-) for ME, I think on balance, I would INSTEAD opt for the Kestrel 48 in the Small to Medium frame size (S/M). Just as an FYI, according to the Osprey web site, if you do this, the actual capacity of the rucksack drops to about 46 liters. The width and depth of the rucksack body are identical. They reduced the height by 2 inches to shorten the back (torso) panel for shorter torsos (like me). Thus, in my situation, I might be using a Kestrel 48 S/M adjusted longer, instead of a Kestrel 48 M/L adjusted to its shortest ability.
The weight difference between the Kestrel 38 and Kestrel 48 is ONLY 3 ounces (80 grams). The weight difference between the Kestrel 48 M/L and S/M is also only 3 ounces (80 grams). So, weight total pack weight difference ought not be the deciding factor (IMHO). Fit, comfort, carrying capacity, and features that appeal to you should decide the model to choose.
See here for details on this:
http://www.ospreypacks.com/en/product/mens/kestrel_48?tab=specifications
BTW - If anyone is interested in my slightly used, well-loved, and well maintained Kestrel 48 M/L in green/grey, send me a PM. I will even include the not used Osprey 2-liter water bladder, and the Osprey Transporter duffel bag for checking the loaded rucksack on an airplane. I would replace it with the Kestrel 48 S/M as discussed above. I accept PayPal...
Finally, I have no business or investment interest in Osprey. I just happen to love their products. In fairness; however; it MUST be pointed out that there are several well known and well made rucksack brands seen frequently on the Camino that offer similar sizing ranges and fitting flexibility, depending on model and capacity. These include, but are not limited to (alphabetically): AARN Packs (NZ/AU), Deuter, Ferrino, Gregory, Kelty, MEC (Canada), North Face, Quechua (Decathlon's house brand in Europe), and Tatonka. Sorry if I left anyone out, but I did not write this down when I was on Camino.
Regardless of what rucksack you choose, You need to check that the torso is vertically adjustable for shorter or taller chest lengths, and that the shoulder straps can pull the rucksack UP and IN to your shoulders. Oh, and it sort of goes without saying, a sternum (chest) strap is a must especially when handling steep climbs and narrow paths up and down some of the higher elevations on the Camino.
Thanks for "listening." As always, I hope this helps someone.