If you really want safety you wont cut them at all.
That aside the thing that is most dangerous about chopped springs is the fact that nobody uses shortened shocks. That allows the spring to simply fall out if the suspension is fully unloaded.
This is the catch 22 of chopping springs because by chopping you cause the car to bottom out the suspension frequently,that causes a bounce,that causes the suspension to unload and your spring may fall straight out.