Anyone trying to Backtest, then these are the few points might be useful. Breakouts per se is low Probability, including Opening Range, in respective of the time frame, if one is not aware about overall Context & Price Action.
First thing is to consider is Overall Context, specially last hour context, this itself will filter many bad trades , as Open is nothing but the extension of the previous day move. E.g if Previous two- three days are trend days on Daily charts, then proabability of success of range BO is High compare to if we have Trading Range kind of PA, where most of the BO will fails, so ignoring or fading the first BO ,a better play.
Second thing is Gap, as Gap can be Large, Medium or Small , again within the given context as Gap can be breakaway or exhaustion also. Most of the Gaps within the range of Previous day get filled, or Gap late in move will reverse , or Large Gaps expands wherein Small Gaps contracts, these are the few examples of Gaps...understanding of Gaps is Must in successfully trading the Open.
And Finally the First Opening Range Bar, here the kind of First Bar we have again this is one information we have that given day and we have to make decsion based on that first bar itself, as bar can be Trend Bar or doji or Bars with both side tails. On Trading Range Day , fading the doji or Bars with tails make more sense as most of the BO in TR Day will fail, so either fading or ignoring first BO will save many bad trades, wherein on Trend Days if first Bar is strong, increases the Probability.
Advantage of Trading Open are obvious as around 70% of the day Day High-Low determined in First two Hour, in that around 40% of the day within first 30 Minutes, so if one read it right then there is great Potential for the swing trade in the direection of the Move. Second Moves in Open are fast and big so again Great Math in terms of R:R
Good Luck.