kuj, your reasoning sounds valid to me.
i switched my FB team to zone/press a couple years back. my theory was that it would spare me some of the fatigue that my fb offense is causing.
but what i noticed is that i was forcing fewer turnovers (as you might expect), and that was bad news for my fb offense as TO's are the best way to start the break.
so, im sliding back toward straight press.
and lately, i havent been able to beat my way out of a paper sack. so, not that sure if that is any consolation, but im as stumped as you are on this issue. let me know if you figure out the answer.