Of the 16 instances 10 saw an intraday drop of 1% or more from the opening price and 6 did not.
12 of the 16 broke below the lows of the 1st half hour of trading at some point during the day. Shorting that break and holding until the end of the day would have resulted in 6 winning trades and 6 losing trades.
5 of them broke the lows of the 1st half hour after 10:30am. Of those, 4 went on to close even lower on the day. The lone instance that rebounded closed almost 3% higher, though.
So far I've yet to indentify a sizable edge for trading a gap this large on an intraday basis. I will update further if I do.