I decided to go with a cats whisker VOR Antenna on the vertical fin; I'll put red plastic tips on the ends to protect against errant eyeball injuries. The antenna I bought from Wicks was way too wide for the vertical fin. I cut some Nylon stock so as to stack the dipoles slightly vertically; that allowed the antenna to fit in the .85 in vertical fin width. I doubt there will be much loss in efficiency with the 1/2 inch offset. I fabricated a .030 steel channel and welded it in place, so the fabric can wrap around it. I also welded two doublers and drilled and routed them out so the VOR cable could pass through the ribs without compromising strength. Next step, fabricate two aluminum plates, which will attach via nutplates to the channels, and which will also secure the nylon block.