Wayne, as you know, I am building the 7pi-18 for my older son, and 4pi Theatre for myself. Adding the 7pi mid horn later is intriguing. Would it hurt for me to build the 4pi Theatre box, but not make a cutout for the H290 horn, instead sitting that on top? Then later just jack that up and slip the mid in between.
Or would you suggest just building the 4pi Theatre as per plans, with the horn in the box, and just stick the mid on top?