Good mornings are definitely not appropriate for everyone. I like the way Rippetoe and Kilgore deal with them in SS. (Although I will have to say that I have done and will do good mornings without a 1 RM squat of 300 lbs.) I have long hammies and good isometric torso control, so it isn't a big deal for me.
As for your question regarding bar placement, I have always placed the bar in the same position I use for squats--and I'm a high bar squat kinda girl. With my turkey neck, this is nowhere near my C-7. The bar is on my traps. The illustrations in SS appear to show the bar on the traps, not what I'd describe as "in the neck." I am not sure what Rip means exactly; you might go here and ask him to clarify it for you.
An aside, I also personally like to do SLDLs. Again, much more fun if you have good hamstring flexibility. But they are for more advanced athletes who have quality movement and control.
I would never prescribe a weighted good morning for someone I've never personally instructed. There is just too much potential risk involved making sure that lumbo-pelvic awareness and control are there.
That said....I do like to teach anyone the Waiter's Bow (basically a good morning movement, double and single leg) with a dowel and 45 deg hip/torso extensions. I think it is essential for everyone to learn to distinguish spinal flexion/extension from hip flexion/extension, and learn to isometrically lock a neutral-spine torso to the pelvis. There is some data to show that people with LBP have trouble distinguishing spine/hip flexion. Thus, the Waiter's Bow, i.e. good morning / sldl movement, if learned properly, should be protective; and an additional lifting strategy in cases where the squat cannot or does not need to be used. It beats the hell out of stooping, the lifting strategy many people use and the only strategy that has been compared to squat lifting in the literature (that I can find).
I would only add external resistance to good mornings on case-by-case basis. Most people should be fine using bodyweight only for 10-20+ reps and several sets. If you are a competitive lifter, you may find 35% of your 1 RM squat appropriate
I am not a fan of rounded-back lifts. I can understand the argument of preparing the body for those times when a rounded-back position is the only lifting position possible; but I still have a hard time putting a bar in someone's hands or on their back to intentionally train that movement. The risk is too high for my taste; I don't do them myself . I could see doing some spinal flexion/extension over a swiss ball; the anterior shear forces would be reduced and the passive structures controlling the spine into flexion supported, if one absolutely determined they needed to train the spinal extension musculature dynamically.
And I know, there's always that one dude, who's done them for years, that swears by them. Just like there are people who've smoked like chimneys and drank like fish for years. A few outliers survive. Many more do not.
Personally, I think most of us can get by with focusing on isometric torso strength. The musculature is designed to work most effectively, in the context of all other torso stabilizing structures, against heavy load, isometrically. My motto is: Flex and extend a loaded spine at your own risk.










