Shorting only FAZ or FAS just for the compounding error to kick in slowly is
too risky. One strategy is to short FAZ and FAS with the same amount of
money at the same time. Suppose that you had 150K and used 50K to short FAZ,
50K to short FAS, and kept the rest 50K in cash.
8/8 FAZ 80, FAS 12.50
9/23 FAZ 69, FAS 10.50
The current return is (50K-50K/80*69) + (50K-50K/12.5*10.50) = 6875+2000=
14875. And you didn't need to do anything. Of course there is a RISK!
Theoretically, FAS can lose 100% and FAZ can grow to infinity. For example,
assume that the finance sector has 10 straight 3.33% decline in two weeks. We
have (1+10%)^10=259% + (1-10%)^10=35%, which is barely close to 300%. That's
why you need to 50K in cash! So as long as FAZ does not grow to 300%, there is no
risk of margin call, but you have lost 50K for sure:-). Another direction that
FAS grows to 300% is even smaller under the current economic situation.
You need a strong heart and be prepared to take some temp loss.