I had chance to build the power circuit on the latest RoBonnet today; looking for a steady 5V drawing 3A regardless of input voltage (up to 24V).

The minimum components were assembled, inputs attached to a bench supply, and the output attached to a cheap variable load battery tester (https://smile.amazon.com/gp/product/B01E6YSGPG); a device offering slightly more control than the simple 2 ohm resister I'd used previously.

After powering on, checking the output voltage with a Fluke multimeter, adjusting the load and input voltage, I can conclude ... it works! Although I did tweak the components for this version, I'm sure the changes in power layout is what solved my previous issues. I wish I understood it more though.

Next step is to assemble a more complete board.