it is very easy to get as much treble back as you want by just filling the housing with cotton wool. some time ago i made this with a modded sr225i venting all holes of the drivers but filling the whole housings with cotton wool. result is a bright and analytical sounding headphone with unbelievable speed and precision, some of my friends found it to rival my beyer t5p. just yesterday i thought of rebuilding that one as i had used the drivers for another project in the meantime. only be sure to use a fine gauge so using the same amount of cotton wool for both sides.
Huh! Might try that. Although I'm deathly afraid to open them up though :P but it might be worth it. Thanks for the help!