hold on ill make a sideways view of that picture so its easyer to see. but this box is going ontop of a seat, that describes the odd shapeWhat are you trying to get? That's not a very good picture to describe what you're looking for...
not big at all... about 9", im running infinity 1050W 10"s under them right now and i can tell the box is too smallhow much room is under your rear seat? i dont know the mounting depth on those 12's, but i think you woul dprobably find a way of fitting those 12's without doing some contraption on your seat like that