It seems that Storm puts more faith in the Double Agent for heavy oil... the Special Agent is listed as a Medium-Heavy oil ball.
I think most people don't see true heavy oil, so the SA wouldn't be a bad choice for "heavy oil" just be sure to put the appropriate layout and surface for a juiced condition.
--------------------
"A word to the wise ain't necessary -- it's the stupid ones that need the advice." Bill Cosby
"Never argue with an idiot. They bring you down to their level and beat you with experience."