Thanks for the suggestion. I like your reasoning, but am a little iffy about the medium range just because Spiritwall is a little more powerful than Wall of Fire, IMO. Forcing a Will save or fleeing in fear, causing damage and possibly a negative level for anyone going through it, stopping spells and giving total cover, and allowing no save to avoid being caught in it - that's a lot of stuff! Unfortunately it's sure to be a while before T&B errata is out (I think), so there's no official help either.