@mdb1056 - Thanks!
@scorban2 - maybe think about it this way; you deadlift a barbell loaded with a couple hundred pounds. Standing there with your back straight and shoulders back, you can hold it fairly well - most of the load goes through your frame (skeleton). Now, lean forward a little bit. The load on your upper and lower back is barely manageable. Now, still leaning forward, try to bring the bar in to your hips. You can maybe move it a bit, but your upper arms will quickly give out. This is the load your back and shoulders take if you aren't effectively putting the load on your frame instead of your muscles.
I've heard all the various tips that work for other people (hips up, push chest forward, shoulders back, keep your chin up, etc.), but for whatever reason, none of them clicked for me. I thought I was there, but the fatigue in my upper arms proved I was not. By paying attention to the fatigue in my upper arms, then straightening myself so this load shifts to my frame rather than my muscles, I found something I could first visualize, then make happen. The reduced load on the back of my upper arms is immediate evidence as to whether I'm doing it right. I'm basically saying the same thing others have said about stack, but maybe in just a slightly different way.