This might of been the one you saw (not uneven ones, just saggy):
https://forum.oneclickchicks.com/showthread.php?t=28371
There's also this one from 2006 if you haven't seen it already:
https://forum.oneclickchicks.com/showthread.php?t=32409
There are some other recent threads that are strictly "boob" threads (first five pages of the Sexy Amateurs section) but none of them seem to have the uneven theme.
Slick