The NPatch introduces Iron Curtain functionality on a weapon basis instead of just superweapon. The effect just requires IronCurtain=yes on a warhead. Damage on the weapon controls the length of the effect in frames. However, it is not recommended to set the effect to less than 150 frames unless you have a new animation to use for the effect. You should also keep in mind that this effect does take Verses, CellSpread, PercentAtMax and other warhead tags into account.