Yes, I had played around with expanding the horn in an attempt to move the LF rolloff as close to 160Hz as possible (the highest compromise I'll tolerate for X-over to a dedicated sub), and wound up with a mouth of 30.5" x 15.5", but with only 13" of depth. Shouldn't I need 21.25" of depth for 1/4 WL of 160Hz? The trouble with a 90-degree horn is that the mouth widens 2" for every 1" of depth added. The rest of the fantasy was to coaxially mount the HF section inside the midhorn's mouth, using a pair of up-ended, trim'n'glue P.Audio PH2510 horns to create an unbroken vertical array to the next midhorn/high pak. Voila, vertical line array!