i did four on the old 225 and 2 on the 60.
i also seal the ear foam that bring out bass as well
now the 325is took me a year to voice. felt and tape and socks, i found that the 325is needs to be further off the ear than the other 225/60 I have fussed with.
The bass extension has always been there on the 325is just needs to kick it up and that is done by seal before vent and the 2500Hz leading edge sharpness is brought under control by position and seal now all i have to do is vent arthroscopicly .
the 325is voiced to my ear is hi end detail and bass extension the heavy alum does wonders for dampening and acoustic mass transfer loss is reduced. I plan on one hole at a time, 2-4 max. Bill likes to remove the white screen on the 60 i have not tried that have you tried venting just some off the white screen holes
these are the felt and sock ear thingies on the 325is... I use "special 33" vinyl tape from the hardware store it is softer and more flexable than cheep stuff ..i use felt furniture mat.. it is the green you see , and this keeps the white screen further off the ear..that was all it needed to kill the 2500Hz leading edge sharpness that get called "bright" note the 325is is louder than the 225/60 and the brightness is fixable which leaves bass and hi end detail...
remember kids voice the canz to your ears and nobody else. these are merely suggestions on what to try. i say seal foam then vent as necessary. 1 at a time. I have small ears that are paralel to my head and these fit around my whole ear. never on so that is my Grado 's never were uncomfortable with L-cush.