Hi jcarff
I have been thinking about this and wanted to put out a diagram, but you have done it thank you. I did have my Hereink antenna mounted along the z axis, when I was testing it. But according to @Philip you have to mount it along the Y axis with the 15 degrees offset facing the ground on each side of the craft.
When we a flying the craft is either flying away or towards us most of the time. This means the donut effect of reception area will not cover the controller? Please try it out and keep all of us informed.
Great job, you have done so far. I wanted to try this my self with my trusted Mi drone by piggy backing the Herelink but was concerned about the power draw, and safety issue raised. Also not happy to destroy my trusted flyer for the time.
Excellent work, thank you for sharing your work.