A bellcurve for d20

The thought just struck me: what would the impact of using alternative dice rolling have on To-Hit Rolls in D&D / Labyrinth Lord / Castles & Crusades?

The dice mechanic I'm looking at to generate a bell curve for the roll wouldn't be a 3d6, but the JAGS use of four modified d6s rolling 0 to 5.

The bellcurve looks like this (courtesy of anydice.com)

Now I have to figure out what that means in terms of hitting Armor Classes (Ascending or Descending).