Both eyes open. I'm lucky in having a farsighted left eye and a nearsighted dominant right eye. So, when I shoot target focus the sights aren't that blurry--more like what people describe as intermediate focus. I've experimented with closing an eye on very long shots. It doesn't help, and takes longer.
The OEM dimensions on Shadow2 sights are: Rear 0.125" notch, FO front 0.120" wide. I like this combo.
On long shots, the following have to all be acceptable, and under match pressure--especially after a 25yd sprint--that's not a given:
1. Sight alignment and aim point
2. Stable sight picture after transition and split
3. Trigger press
4. Knowing your POI at a given distance
Great discussion! Let's keep this going.