You may have to keep your torso level to avoid a back angle.
If the head is elevated more than your torso, you'll get headaches, nausea, dizziness, or other physical issues. What's your head-to-ankle alignment? Is the angle correct? Does it need to be adjusted? Why? If you have a high neck and/or a high head-to-thigh alignment and your body is leaning forward, you'll feel tense or stiff in your legs and arms.
Are you leaning forward? You may not want to be. I'm sure you're trying to get a better understanding of body alignment in general. I am leaning forward. But why? I am not leaning forward to lose weight or have poor posture. Yes, you are. Or maybe you're in a position where your body is leaning forward to get a better overview of what you're doing. Maybe you're in a hurry. Maybe you feel like your posture is good, but your body is leaning forward. Or maybe you are really interested in seeing what you can see on your back at a certain angle. You want to change your body alignment to make yourself more comfortable and ensure that your posture is effective and balanced. If the body is leaning forward but you are still feeling tightness in the legs, you might want to ask yourself if that is more a problem in your hips or in your neck.
If the body is leaning forward but you are not getting a good overview of what you are doing, you'll probably want to ask yourself why you are getting that information, since it's not going to make you more comfortable. If you are in a position where you are really trying to get a physical overview and you are leaning forward, you'll know now that you are aligned properly now.