The table says 3n-4-1-2 which has always worked for me. I love me some butterfly too.
3n-4-1-2 is the same as a 3-5-2 with a red arrow on an MC. Do you have an MC that has AMC positional eligibility? If so, play a 3-5-2 and move the MC to AMC if he switches to a 4-4-2 or just give an MC a red arrow. Makes sense?