I just received a pair of K550's from a fellow Headfi'er... I have found that I fit in the small head club. I use the headphones at the 1 setting and found the fit to be pretty good but not as good as putting slight pressure with my hands and hearing how things could be..
I dont really want to mangle my headphones with bending.. also I think bending the center of the band would lower the ear cups on my head.. I did however slightly (I mean slightly) applied small bends at the number 1 on both sides.
I slid the band open to its largest setting and rested my finger at the edge of the foam on the headband.. at that point is where I applied a small bend (really cant even notice it) on both sides.. I feel being farther down on the band pushes the cups in instead of down and in with the center bend..
not sure if anyone wants to give this a go.. but if you do let me know what you find..
BTW these headphones sound fantastic..
I recently purchased a Nova N1 to go with my Cowon S9.. I feel the Cowon does a much better job with these than the N1..
N1 beats out the Cowon however with my reshelled Shure E530s