I'm moving Dwalin from the breadboard stage to prototype in the enclosure. As part of this, I'm setting it up so that the Pi can turn off power to the Feather in order to run the Feather from the LiPo battery once a week. Unfortunately I've run into two problems: 

1. I didn't set it up so that I can either reach the LiPo JST connector when everything is mounted into the enclosure (even with the top off) nor so that I can reach either the reset button on the Feather or on the Latching Relay Wing. For now, until I get a reset button for the Feather accessible, I've just been using a jumper to manually reset after I get everything plugged in.
2. A bigger issue is around startup draw from the Feather, particularly in the context of the Pi disconnecting input power going to the Feather. If I have the LiPo plugged in, things are working correctly (the charge indicator on the Feather tells me that power is coming in or not and both Pi and Feather work as I expect through a power off/on cycle of the Feather initiated by the Pi). If I don't have the LiPo plugged in, when I command the Pi GPIO pin connected via transistor to the relay to open the +5V to the Feather the Feather will simply shut off as expected. When I command the Pi to return power to the Feather, the Feather starts (f.e. expected output to the OLED), but the Pi reboots at the same time. I think what's happening is that the startup of the Feather is briefly drawing enough current to trigger the brownout detection circuit on the Pi and so the Pi is halting/resetting.

I tried putting a 47uF cap between +5V and GND, but that wasn't sufficient to carry through the transition.