@GertSanders
Thank you for the reply! Was the atmega doing some clock critical tasks when it went below 2v? I am thinking to attach BME280 (Pressure/Temp/Hum) which also operates in the same voltage range, but not sure if the I2C will be working properly when atmega goes overclocked.

@26872, It's my first post here and I had to register so that I could give you my regards for your work and for sharing it with us! Just ordered a batch of your v2 boards.

I have similar design sensors running on proto-pcbs, but your ready-made pcb makes everything much more convenient.

Just had a question on stability of running regular Arduino 8mhz internal clock bootloader for prolonged time. Anyone tried this and had success running the 328 down to 2v (or so) @ 8mhz? If this is a doomed idea, I will have to attach the boost circuit to this design, but it would be nice to avoid all that parasite current consumption.