@User: Most of my difficulty with it comes from poorly-worded documentation for ngspice. To understand it, you have to experiment with it. I haven't had the time to experiment with it, which is why I have left the monte carlo equations unfinished in the sky130_fd_pr library. If you have recommendations on how the existing spectre parameters can be systematically (i.e., by python script) converted into the ngspice equivalent, I can take a stab at fixing the repository.