RE: What about two open eyes
Good point Rob,the dominant eye is the key.Both eyes open is best but if your not using your dominant eye or have your bow matched up to your dominant eye,it could be very difficult to shoot this way.
It does help in low light a tremendous amount when eveything is set up right.It also helps on those really close shots that you can't see anything but hair in the peep.Both eyes open will allow you to put the pin where it belongs on these kinds of shots.
I know if your not used to it ,it is difficult but like anything else.Change may be for the better but takes some practice to master.