It's time to start planning the building of the boxes. I'm considering one box for the woofer and the H290 on top. I would like to put the boxes on top of my 18" subs. I can't find dimensions of the 4pi on the forum. How big should the boxes be and to what frequency should they be tuned (how long ports)? Do the ports need to be on the front for this design to sound it's best?