I must admit that I find shorting incredibly difficult. I have been using Q for a couple of years now and have managed to develop a few algorithms that seem to (comprehensively) beat the market in the long run (according to backtest results, anyhow), but they are all long only.
I have tried all kinds of approaches to incorporate shorting into my momentum and fundamental strategies, but none of them was ever profitable.
Yet obviously it can be done, since it is a requirement for the Contest and there are many brilliant algorithms competing there that fulfill the criterion and at the same time achieve good returns.
I completely understand that nobody is willing to reveal the secrets of their success, but just a tiny hint at what broad strategies and approaches work in shorting or where one should look for inspiration would be greatly appreciated.