Thanks guys for confirming that these do stretch. There must be some flexibility in the plastic construction then or at the joints. I should be getting these ultrasone dj headphones soon as I do think that they could be the best closed+isolating headphones sonicaly I've come across. Their sense of depth is what puts them above the sig pro in my eyes and I didn't find them have a recessed midrange in the grand sense of things.
What did the construction look like when you dissembled the headband - what did you do to tighten them?
Lastly, is it just me or are the pads different from the sig pro. I find the ones on the dj to be more comfortable for some reason.