I still have issues with my form. I have no idea why I insist on keeping my head down after I check my grip and when I start to pull. I do know though that my lower back is straight, even though my upper back is not ( which shortens the pull ).
Here's the clip of my 475# deadlift PR. I felt like I had another 40 pounds in me, but my body was finished after this one so I listened to it and stopped.