Here is the PCB rendering in KiCAD

Here is the PCB

On the left are the screw terminals to apply the 12V.  C1-C6 are the input capacitors.  The transistors are SIRA20DP.  They are controlled by a MP18021.  Why the MP18021?  It can handle -5V on the switching node.  It also has the integrated diode for high side driver.  The inductor is a 1uH SRP1265A.  The output current is measured using a 0.001 Ohm sense resistor, with Kelvin connections to the INA180 current sensor.  There is a small output capacitor.  Then, to connect to the supercapacitor (and make sure I don't have ~200 Amps in the event of a short while probing), I used a 15A 0ZRN1500FF1A polymeric fuse.  The terminals on the right are for the load.  The 8-pin JST connector connects to the controller.