AR-15s
Yeah, I like 1/3 cowitness as well for that reason. Red dots will be visible in the dark, but if the ambient lighting is too dark, you won't see anything in the room. If you are able to add a light, make sure to have the red dot at the correct intensity for when the light is on. If you ha e it dim for dark light use and turn a light on, it can wash the dot out.
This is the only picture I have of one of my red dots. It's a Leupold RDS