Still very much enjoying my custom hitch bike rack. Bikes are very much a part of the camping enjoyment for my family. Having a tandem further complicates matters but this has solved that for us. Towed up/down, all around the Sierra's this past couple weeks, including an 11 mile, 6-8% grade mountain road better known as Kingsbury grade. Nothing but great stability.
I'll say that I didn't make this upgrade in isolation. I was aware of the potential pitfalls. I have additional weight on my tongue in the form of upgraded 2x 6V batts, and a Honda eu2200i genny. Partially to round out the trailers capabilities, but those added items also reinforce having sufficient tongue weight for stability. Also when I sealed the rear bumber to shell interface, I added additional mounting screws between the shell and chassis (under the rub strip).
The setup is exceedingly stable as I can see the bikes in my rearview camera. I still added a couple bungees (blue) between the bikes and rear awning supports as additional damping and support.