Thanks for the link, Ian! Article is downloaded, I'll let you know what I think when finished reading later this year.... Since the considered cones might be paired with a 2" horn/driver combo, I'm hesitant to go smaller than 10", unless I decide to use an adaptor for a 1" driver instead (entirely feasible). The HF horn I have in mind is the DDS CFD2-25, with an interchangeable 25x30 degree coverage, turned sideways for the 30-degree application.I took example for the "Transitional Throat Waveguide-type Thingy" from the EV X-Line 3-way box. The vertically stacked pair of 8" cones have what I seek.