There's nothing wrong with naked shorting. You can see this if you drop the distinction of commodity and currency, i.e. just turn the chart around. If you're over-leveraged, you can get a margin call whether you're long or short. All successful (profitable) speculation will decrease volatility and all losses will increase volatility – it doesn't depend on the instrument as long as you know what you're doing.

Back on topic; I've found that undervolting is almost never mentioned. The performance per watt seems to be the most important metric, even before the initial investment in hardware. Comparisons are usually topped by mid-range cards, but that's because the high-end cards run at higher stock voltages and frequencies. You can easily double the FLOPS/W by undervolting and underclocking, e.g. with ATI Tray Tools.