Winseer, Regarding the gold trade... I was comparing margin required (and a few other things) to profit locked in. The spread seems to work pretty well.
You are right regarding your cotton idea. I have a friend who does something similar in another commodity... But your risk is always whether or not they will deliver. So you have to know who you are dealing with... Or it could get ugly.
I'm always looking for those low risk, good return, offbeat trades. If you foresee interest rates staying low, you might want to compare margin required vs. Profit locked in.