Yup. 4-1-3n-2 is a gud counter for wide diamond. The 3 MCs will take advantage of the no MCs from his side. Even narrow diamond should work. Just one variation from what wiesse said, in narrow diamond u will only have totake a central MC out, and put an AMC so that ur AMC keeps his DMC busy, so that he can neither help his defence to take on ur 2 ST, nor go ahead to attack and help his forwards.