Hi did you figure this out? I’m currently using a Powerboost 1000c with an On/Off Shim. I have the 5v (USB) power running to the Powerboost, then the power boost feeds the power to the On/Off Shim (instead of directly to the Pi).
I’m using the PowerBoost to handle powering (from 5v usb, or battery) and charging the battery. I’m using the On/Off Shim to handle clean shutdowns and my devices power button is hooked up to it.
I haven’t tested to see if it just auto-magically shuts off the pi on low battery (I don’t think it does?), so that may be issue #1.
Also, issue #2, the powerboost itself always thinks it’s still on (because, well, it is). The power gets cut on the next part of the circuit (on/off shim) so the Powerboost still has it’s LEDs active. What’s the best way to wire that up to switch on/off the powerboost too?