I understand that it is better to cast Foul in UI. As such I can see the merits of using 3.x rotation there so that you are not forced to use Foul in AF during 4.0 rotation or worse, lose the Foul stack. But the same thing is true for if you do too many 3.x rotations and/or don't get enough procs to extend 3.x rotation, and end up not being able to Foul in UI.
