I think my schematic is ready. I realized this morning that all the pins are normally floating anyway, so I should just leave all the ones I'm not using disconnected. The expresscard spec does say that the SMBUS pins should be pull up through a pair of 5k resistors, so I'll route that but the NVMe PCB doesn't bother so it's probably not critical. My first hurdle is choosing the SMD size. I think 0603 for the capacitors, but we'll see if that changes when I go to pick parts. Maybe I should go pick parts now... I also need to understand polarized capacitors (and the associated footprints). I'm confused because kicad wants me to use [electrolytic capacitors](https://klc.kicad.org/footprint/f3/f3.3/#_smd_electrolytic_capacitor) which have their own footprint, but I don't see any capacitors that look different in the powerboost 500 circuit. It looks like the schematic might differ from the actual PCB? Or maybe it's an electrolytic capacitor in the schematic but populated as a ceramic capacitor? The datasheet for the boost converter only has 1 ceramic and 1 electrolytic, whereas Adafruit has 1 ceramic and 2 electrolytics.