I think what you are mentioning with this cable is exactly what I want to do. You say you were unable however to control the audio levels? How come they could not be controlled either through the h4n or in the DSLRs audio levels directly (I know not all DSLRs have the capability, I believe the 60D does, though its likely not very good).
I really want to download ML, I’m just nervous to do so! If something happened to my camera I wouldn’t have the money to replace it anytime soon!