A quick hit from the LRB Facebook page.....
Not sure if everyone understands how great of a movement that good mornings are IF done correctly.
By correctly I mean with reps and using it to stretch the hams and glutes, and get a strong contraction in the glutes on the concentric. I can't for the life of me figure out why guys work up to 500-600 pounds in the good morning. I have yet to get to a meet where the good morning was one of the lifts to be done.
At a 600+ raw no belt, no wraps squat I rarely go over 225 when using good mornings. If you really want to get the most out of this movement then back off on the weight, get 4-5 sets of 10-12 in and use it to build the musculature of the hams, glutes, and erectors.
Don't turn it into some kind of half squat/half bend over movement. Stretch the hams and glutes with it, and then use the glutes to push through at the top. Very much like how you lock out a deadlift.
GM's cover assistance for both the squat and dead. Throw in a front squat and a row and that literally covers everything you need for the squat and pull in terms of support work. If you wanted to be even more complete, a single legged movement in there will give you some pre-hab work and keep you mobile.