If you're continually missing PR attempts off the floor, try using block pulls off 3-4 inch blocks. This will allow you to challenge your hip and back position at an angle that mimics where the bar will be right after you get it off the floor.
Experienced lifters should do these with a quick set-up and a rapid descent.
Are you 30 years old but feel like you've got the spine of a 90-year-old well digger? Michael and Cassandra can cure what ails ya'. Practice their deloading drills regularly and your spine will soon be as straight and springy as a young poodle dog's tail.