Hello fleinze,
What about this project? Your sensors still working?
I'm trying to build the same but I have some problem to change the efuse value:
"I changed the efuse value to 0x07 (BOD off)"

I' dont know how to edit the boards.txt file and how to install it in the arduino pro mini.

Could you explain the procedure step by step or link me a good complete tutorial ?

Thank you very much