Hi, Beto... I am presently building 3 pair of Pi speakers.(1) I am building a pair of 4pi Theatres for my own use.
(b) I am building a pair of 4pi Theatres for my older son for his library/office/listening room,
(iii) and building the 7pi-18's for his living room.
Presently he does not have two adjacent corners to use the 7pi corner horns as designed. What Wayne suggested to me was to build bass bins identical to the 4pi Theatre cabinets, same ports, but simply put the Eminence Magnum HO 18's in these cabs instead of the Theatre's Delta 15's.
Presently I am in the process of cutting wood for three pair of cabinets 36" H x 24" W x 18" D. I will also build the proper 7pi-18 bass corner bins for my son to later simply remove the woofers and crossover from the 4pi bins and put into the corner horn bins.