Tom D. Indeed we avoid aligning the geometric plane of the XO panel normal to the velocity propagation wave. The vertical boards are aligned to present minimal area to the velocity wave. Adjustable resonance control is an attractive mechanism, both for the XO and the drivers. My approach tries to control the forces without the complication of user adjustability. I have prototyped tunable control and the future could lead there. The combination of bronze and Panzerholz works very well to dissipate energy while providing considerable strength. Progress is being made.