I tested ( 433 Extreme XX-4 ) this in League One with Sheffield Wednesday - Possession seemed low in most games, rarely getting above 50% and often low 40s with 2 35%s. Only 3 games I had more possession than the other team, these were 51-54%. I am a League One team though.
Having said that, in the short test so far, not holiday, it rarely concedes goals. It also seems to create quite a few chances per game.
I feel this is a strong tactic and I will attempt to do a full season test on it.
Good work!
EDIT: Possession stats picked up as familiarity was gained. Also, I played a cup game with 5 of the starting line up from my under 18s, against a side from the same division, and won 1-0. This tactics is insanely tight at the back compared to others I have tested. More enjoyment watching it too.