BTW Tyll,
The only picture I saw of your dummy head had funny shaped ears (like realistic molds) yet you reference a standard dummy head for which the pics I have seen show a simplified ear geometry. Which is it really in your rig?
I am asking that because I have been playing with simulation of ear shape / impedance effects on headphone measurements and it's rather significant above a few kHz. As such, beyond using a DF or FF or ID equalization, what matters the most is that this target curve corresponds to your actual measuring apparatus.