I have uploaded a new attack table and critical table for Spell-slinging. These tables cover attacks like Magic Missile (and could probably be used for Lightning Bolt or Fireballs, but I may make those tables more powerful).
Some terms may be needed to understand this document, as I plan to eventually release a S&W Companion called "Swords of Abandon", heavily influenced by early Rolemaster and M.E.R.P. The new terms are:
OCF: Offensive Combat Factor (for Fighters it is level x5, Clerics level x2, and Magic Users level x1.
DCF: Defensive Combat Factor (for PC/NPC's this equals DEX - may boost fighters later, for monsters it is currently HD x5).
Hits: Hit points, to boost PC/NPC, add CON to HP total. For monsters, hp x3.
SCF: Spell Combat Factor, this is the Spell users' DEX plus level x5.
This is all a work in progress, so these things may change as I refine the rules.
You can download the Spell Slinging pdf here.