Different damping materials have different effects on treble. I've also tried tea bags and found them noticeably less suited than alcohol swabs for this mod. I'll try to get my hands on some 3M micropore tape to compare its effectiveness to alcohol swabs. The rear vent mod isn't likely to change treble, to my ears it just fills in the low end a bit. I used precision screwdrivers to drill. First use the smallest (1mm) crosstip to widen the opening, then use the smallest (1mm) flathead and carefully drill about 2-3 millimeters straight in. The plastic doesn't offer much resistance, so it should take just a minute to get the job done.