Virtually all retail traders (and a very high percentage of institutional traders as well) trade the ES S&P E-Mini contract. It has extraordinary marke depth and one tick liquidity, so it doesn't have the slippage problem that the big contract has. Also, the big contract has a better spread, so with the current volatility I don't believe that slippage you mentioned is too extreme.
That would surely be lucky for our eastern investors. It would bring in a flood of money from the sovereign wealth funds to save the day