Word of caution. I have noticed with the cheaper glasses, when I have sighted in without glasses and then shoot for match with glasses impact changes. My thoughts are that the added lense changes the placement of the image. Much like mirrage, you are aiming at what you percieve to be the target. Take the cheap glasses off and you are back on target. Keep this in mind. Also the way the glasses fit your head, you want to be looking through the same place on the glasses everytime, and you want the glasses at the same angle to the scope, and same distance from the scope. When adding glasses you are essentially adding another lense to the scope that is WAY movable. I'm sure many problems have been blamed on scopes rather then glasses. Someday someone will glue the scope to their head, to prevent this, but it's not going to start with me. Maybe Jackie has some insight here.
Paul