I use a 3-3-2-2 formation with the two playmakers positioned centrally but one on the left and one on the right (like the strikers).
GK; Dida
CB: Stam, defence set to high
CB: Nesta, defence set to high
CB: Maldini, defence set to high
RWB: Cafu, defence set to normal, attacking runs forwards and backwards
LWB: Serginho/Jankulovski, defence set to normal, attacking runs forwards and backwards
DM: Gattuso/Ambrosini/Pirlo, defence set to high
AM(L): Seedorf/Pirlo/Rui Costa/Kaka, defence set to low, attacking runs forward and diagonally out to left wing
AM(R): Kaka/Rui Costa, defence set to normal, attacking runs forward and diagonally out to right wing
CF(L): Gilardino, defence set to low, attacking run forward (and possibly out to left wing)
CF(R): Shevchenko, defence set to normal, attacking run forward (and possibly out to right wnig)
Works brilliantly for me, though the defence requires lots of concentration and its based on my style of play.