Take a look first at the SP500 (weekly bars) with the large positions indicated:
http://www.jrbolsa.com/090201ntspsem1.PNG
and then take a look at the daily bars where in this case we indicate the short positions:
http://www.jrbolsa.com/090201ntspdia2.PNG
Obviously, you can open large or short in both.
More soon.
regards,
jr