You been incredible lucky then, there can be many limits that don't get filled cause lack of shares. I have never used getting in the open, I have always waited five minutes first, then split that bar to enter half way. I never chase anything either. And I never place any protective stops before any market opens, that was lesson learned hard way.
Even entering in the first 30 minutes, or entering a non-sim trade at all, quickly becomes a game of Russian roulette, if you place a precedence on risk:reward in these HFT-dominated markets.