hi,
my question is WHY would you want to use a multiwire circuit in the first place? except for a 240V outlet. first, GFCI will not work on a multiwire circuit.

there has been a time or two that i would like to use a 3/C #12 to deliver two circuits to one area but if you every need a gfi down there you will need a seperate neutral.

i just think that its easy and safer to use a single circuit.

-regards

frodo