Now that I own a perfectly fitted pack (McHale), the McHale measuring process was very interesting.
1. 7th cervical(to floor)
2. iliac-crest (to floor)
3. 1 minus 2 above = spine length
4. hip measurement circumference (waist 1" below iliac crest)
5. Elbow to floor measurement
6. chest girth (for shoulder pads)
7. neck size
8. waist size
9. inseam length
10. Degree of physical fitness
So when I got the demo, it seemed too long. Talking to Dan, he seemed more interested in #4-#10 than #1-#3. Those other measurements help him understand my entire body with reference to the pictures I sent. After several adjustments, I learned that I did not know how to properly adjust the stays, and after several adjustments, the pack fit perfect. What is interesting is that my spine has excessive curvature at the top, and adjusting to the curvature, really shortened the direct line measurement. How did he know this in selecting the demo pack without seeing any pictures of me? I sent pictures after the demo arrived. He also wanted me to hike several times with different amounts of weight, with pictures after each trip. He wanted to see pictures with the stays in max length and min length and was able to tell right away that I did not pull the pack material all the way tight in min mode, even though it makes only a 1" difference.
So why all this information? Because no off-the-shelf pack is going to fit well, unless you have the perfect average proportions the pack was designed for, and the maker truly knows how to construct a pack. Now if you have a total packed weight with everything under 10lbs it might not matter much (but I can tell you that even these weights with a little heavier properly fitted pack makes a big difference over 20 miles), it is not a big deal because you don't need much in the way of structure.
I have hiked many miles in the McHale Demo and my own McHale, with different loads and pack configurations. I have never had the slightest discomfort in my shoulders or hips after a long day hike or multi-day trip. The extra 2 or so pounds compared to all my other packs is well worth the weight "penalty;" and it is really not a penalty, it is pure joy now.