@User That DEV/LOT method also makes sense and would make the models more portable to add/remove new models easily. For what it's worth the ngspice implementation seems to be a copy of the HSpice function so maybe there's some more info on the Hspice side. But there is some scaling factor or something missing because the variations are way too large. The trouble is it's really hard to know what is right - maybe we'll need to do some side by side spectre and ngspice simulations for verification once the monte carlo support is complete.