Have you ever looked at developing a system to predict the direction of the gap?? I assume you have.
Looking at trading pattern/direction correlated with %age move during that last 30 and 60 minute period. First thoughts have the last 30 minutes confirming the previous 30 minutes direction but with a greater %age move.
Then go short or long the index EOD.
Of course this would be trumped by any significant data released after the market...earnings by major companies/sectors...national disasters etc....but on average..perhaps it could be done.
Market Data 
Markets 
AI
