If anyone's interested, I've achieved a more neutral sound (subjectively, mind you) via the following reversible mods using the stock pads:
Fixing the hot treble:
Since I don't have a source for the 2mm thick felt that Solderdude used in
his guide, I fell back to another of the tried and true treble remedies: blocking the centermost area in front of the driver (the MDR-V6 does this, so do the newer Mad Dog and Alpha Dog via the 'BMD', and probably others); I cut a circle out of paxmate and stuck it blocking the innermost two circular rows of the driver, leaving only the outermost circular row of perforations free. This reduced the treble to an acceptable level for me without interfering with the mids too much. I reckon you could use other materials like foamie, variable layers of micropore, or even electrical tape.
Reducing the bass hump:
First, remove the grey foam padding under the earpads, this helps fill the dip around 450 Hz. The cups can be opened by removing the 4 screws visible once the pad is removed; remove the screws and gently separate the baffle from the cup, now inspect the driver assembly and note that one of the venting holes in the periphery of the driver has no paper in it. You can either block it for maximum bass reduction, or dampen the vent with some breathable material to adjust the magnitude of the hump; I used 3M micropore tape with good results.
Clarification: This will NOT kill the bass, even blocking the vent completely leads to a slightly boosted bass response, try it for yourself
The results were 'verified' via sine sweeps and other test signals, then with music. I have no test equipment to show you the changes to the FR, so naturally take these results with a grain of salt. I've gone back and forth with these and other mods and settled with these two, sadly I haven't found a way to mechanically fix the dip around 4-6 KHz or reduce the hump at 1.5 KHz so I use EQ to alleviate it some.