Actually A small note. Some people seem to miss that the Mass-Fab can run on incredible amounts of EU/t, since the packets can't be large then 512EU/t and thus will be accepted by the mass-fab without redesigning the environment (well... don't use a good CASUC...).
My Mass-Fab was powered by 20 Solar-Arrays in 1.0. So it consumed 10240EU/t
In my 1.0 world I had a massfab running on about 3600 EU/t using 6 parallel MFSUs (<3 Ice-fed CASUC) and a high voltage solar array (adv. machines addon). I didn't even try to keep up with scrap production.