Got my PCB boards in, here's the conventional power add-on module, I built that up to test. Of course, the switcher I ended up with has the positive and negative swapped, so my jumper wires swap as well, a bit of a kludge. I also found out that the resistor to limit the inrush current is required, without it the initial charge current is 1.5A, more than the other components like the input rectifier can handle. I just have to live with the longer initial charge time for the supercap, a 5 ohm resistor limits the max current to around 1/2A, about all I want to push it to do. The switcher board is fairly large, but the package works great and gives me about 10 seconds of operation with a full charge. I'll probably do another spin of the boards after testing is complete to clean up the leads and perhaps optimize the component placement to try to minimize the overall size.
