I haven't been able to shoot handgun with both eyes open yet. I can't focus and see two front sight posts. It's weird because I'm able to shoot both eyes open with a rifle and ret dot.
That's my struggle too. I basically have to tilt my head so much that it's practically one eyed shooting anyway. It is better, but it's very difficult for me.I learned the both eyes open way during training. Also gives you some input into what's happening around you.
My hardest thing was both eyes open during g strong side-support side transitions. I'm extremely right-side and right-eye dominant, and it was a real struggle.