Quote from viewpoint:
you better hedge the position with cheap, out-of-money options, (short SSF hedged with cheap OM calls, for example) to avoid wipeout. Sooner or later you will wipe out with that kind of leverage and no hedge.
I'm a pure-daytrader, holding no o/n's. I've traded in Datek with the 4x buying power, so SSF's are similar. My main problem is small amount of capital (about $5k) and PDT rule on top of that. If I can freely trade even 6 times a week, there'd be little to worry about. As it is, I'll be opening accounts at 2 brokers who meet my needs. I might trade stocks 3 times a week and SSF's 3 times a week for total 6 roundtrip daytrades.
p.s.: The complaints about the uptick rule are bullshit. Unless you can short at the exact top-tick, you shouldn't complain. With the spreads at a penny apart, if you go short at market, you'll be filled very quickly because uptick only requires 1 penny up. I've rarely missed a short because of the uptick rule. I just went short looking for at least 20 cents on the downside.
If you don't think there is an advantage to shorting on a downtick you really should learn more about it.