Good Mornings - Proper Form?

Just want to do a check on form/technique.
I’ve incorporated heavier good mornings into my routine (along with stiff leg deads and pullthroughs). My back tends to be my weak point and my primary goal over the next while is to get it stronger.

I am struggling to do 3 reps of GM at 150lbs but I can go do stiff leg deads with multiple sets of 6-8 reps at 225 comfortably.
I’m thinking it is related to technique or maybe I should stick with the GM’s at a lower weight and build up to it. Here’s what I believe is proper GM form (taken mostly from t-Mag article):

To do good mornings, approach a loaded Olympic bar as if you were going to do a conventional squat (feet shoulder-width apart, bar resting on the traps). Now, instead of squatting down, bend forward at the waist as far as you can. Push the glutes back. Keep the knees slightly bent. Do the movement slowly and deliberately. Concentrate on the hamstrings. Try to actually flex your glutes, as this will help focus the stress away from the spinal erectors.Keep your head up and maintain a slight upward arch in the back.

It seems there are numerous forms of good mornings Arched-Back, Rounded back, GM/Squat combo, etc.

How far over should I be bending if trying to go heavy? 30deg? 45deg? 90deg? To build lower back strength should I be doing something else? When I see people say their GM is 60% of their Squat is that bent at 90deg? That would seem very tough to me.

Thanks.

with arched back good mornings, stick you butt back until you lose your arch. do not focus in bending, you will. legs straight. with rounded back, i go to about 90degreess bend. you still want to stick your butt back, but also bend the torso on these. you don’t want the weight going way over your feet. keep your knees slighty bent.

Another good way to do GM’s when you’re starting out is to do them in a seated position. For me, it makes my lower back work a bit harder than the standing version. Just make sure the bench you use is secure and stable when you go up in weight.

I think most of my trouble was with form. Yesterday I was not fully compliant with the form in my first post.
Today I went back to the gym and performed more GM’s using lower weight and really focusing on form. They felt different.

I really focused on “lowering by sticking out my butt” and “flexing the glutes”. I think that yesterday I was doing more bending forward and not doing much with the glutes.

The other big factor seems to be width of the feet. The wider the stance the less stress on the lower back.

I think I’ll keep at it and really focus on the form before going too heavy.

Thanks for the responses. More welcome!

You can try a stance with your feet slightly pidgeon toed – that seems to help a lot of people get better “depth” on SLDL and GMs without rounding the back.