Cut the front springs about 4 or 5 coils, depending on how "slammed" you want it, and cut about 1 or 2 less coils on the back than you did on the front depending on how heavy a load you plan on carrying in the back.
Now I vouch all day long for heating springs. But cutting I would never recommend. Aside from removing springs altogether, cutting is the next worse thing. Later, QD.