I wanted to make some Necromancy spells usefull for npc's above level 40, so I increased the spell magnitude to 80 (level 100 npc's can be necro-ed with the Necromage perk). However, I noticed this also automatically more than doubled the original spell mana cost, making the spell not scale so well with the expert/adept/apprentice/novice spells before it.

How do I change the spell magnitude in the Construction Kit without changing how much mana the spell drains?