The biggest problem I have with woofer arrays is the size of space needed to get to the low notes. If I model my current 2 12 inch 15mm Xmax woofers, to get to 20hz, I have to have more than 7 cu ft in the box. For a dual woofer array I would need 14 cu ft box. For four of them I would need 28 cu ft boxes.I don't believe you can get the FR flat or controllably flat down to 20hz unless you vent them. Sealed boxes will be smaller, but won't go as low.
Have you modeled them in WINisD?
Marlboro