Are you using buy limit entry and moc orders Brent ? If so, then the only slippage would be on those odd days when the open is lower than the buy limit order and your fill is somewhere higher than the open but less that the buy limit ? The days of negative slippage and positive slippage may even things out a bit too. Your metrics may be even better than your seeing based on the higher commission you are using but I guess it would be nice to have live results better than backtesting rather than the other way round.