Interesting comment, Lars. I took a good listen to tracks with good sub bass ("I'm So Lonesome I could Cry" form the Cowboy Junkies Trinity Session is particularly good), and I did not perceive any diminishing sub bass. Again, only a cleaner sound, and perhaps better imaging/soundstage. I did do the full mod, and really don't have the appetite to undue part of it. Out of curiosity, is that half, in sections or how did you determine how much blu-tack on the circumference?
My setup may be different, too, as I've done the grill mod and the bass lens with a 3mm wool felt glue-sticked to the cup directly, which prevents the use of smaller pads/rings or sticky-taped to the cup. (see picture). I'm using the Alpha pads right now, stretched over the cups, but may try the Audeze versions later. But, they are sounding the best I've heard so far right now.