Ok!
I'm not sure if 1.8mm or more, and how well I pasted the stickers (I used a toothpick, but did a hole much bigger than 1.2mm, probably 2mm, and without getting rid of the leftovers, since I don't have the right tools).
But the bass is more controlled now, and can go back to higher levels. (Also I'd say bass is balanced in both Left and Right).
The full open bass, wasn't bad anyway. At home, the same time I did the mod, I got some reflektors tubes (R.I.P. one of them now, cos it failed lol) with more bass than the previous tubes I was using. But with the Fulla 2 the full open mod was much more enjoyable (used the phones during the whole week), but still a bit more bassy than I liked (but much less than at home with the reflektors).
So now, after putting some punched stickers, I think I mitigated the bass enough to a good balanced level. (But of course, this is all subjective. And also depends on the music. Some songs have light bass, and they are more enjoyable with full open bass mod, in general "rock". While some others like electronic music with powerful and slow bass that you can already feel with stock K701, were more painful to listen.
@
bluemonkeyflyer
thanks for the value you've added to this mod!