I'd be less concerned about scratching than I would be about the hinge mechanism. The Fostex just seems fragile at that spot. But if it's going to be staying in one spot it's probably not a major issue.
Edit: FWIW, if you're going to be stationary I'd probably lean TH900. If you can demo a pair that would obviously be best. Don't know how well you remember the Sig Pro sound, but if you like the Fostex significantly more it's safe to say you'd choose it over the DJ as well.
I ended up getting a TH600. Still curious about the Sig DJ but the TH600 is cheaper and I think I'll prefer its bass presentation based on what I've gathered from comparisons (subbass rumble over midbass punch). Plus the low isolation will be a plus... It's always awkward when people trying to talk to me have to tap me on the shoulder lol
Now someone needs to buy some of my stuff!