Brother MacLaren said:And it says "determine randomly which one you hit," but "randomly" doesn't necessarily mean 50/50. You could say that a Large creature counts as 4 Medium-sized creatures (based on the space they take up on the map), for a 1-in-5 chance of hitting your ally and a 4-in-5 chance of hitting the bear. A Huge creature is 9 squares, so if it were something Huge, 1-in-10 chance of hitting the ally, 9-in-10 of hitting the monster.
hong said:The fire into grapple rules are idiotic. They imply that all other things being equal, a 20th level munchkin archer has a higher chance of hitting his buddy than does a 1st level blind commoner.
SRD-Combat Modifiers-Armor Class Modifiers Table-Footnote 3 said:3 Roll randomly to see which grappling combatant you strike. That defender loses any Dexterity bonus to AC.
It seems to me that surface area (cross-section) is more relevant than volume here. So the "depth" wouldn't matter, and Large would be 2x2, Huge 3x3, Tiny 0.5x0.5, etc.The_Ditto said:I know the rules support this (ie RAW) ... no argument .. however, I tend to look at Large creatures as 2x2x2 = 8 squares ... and Huge as 3x3x3 = 27 squares ...

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.