Seated Good-mornings rock! I like them as much or more than standing good-mornings. I basically set-up for a typical box squat workout. Once I'm on the box, I place my feet out in front of me (learned this by watching the Westside Videos - nice counter-balance), arch my back hard and lower my upper body as far over as I can without losing my arch (ROM is reduced). You can do these rounded-back as well for an increased range of motion but the weight will drop dramatically. Once you've hit your desired reps (I never do more than 5) you have to box squat the weight back up to the pins to rack it. Like Arioch said, "this is easier said than done!" You need good spotters (may need help) because you'll be whooped once the weight gets heavy. I've done a triple at 405 so I'm probably good for a single at 455. When the weight gets heavy your going to have to grind to get it back up. It can take forever sometimes. Good luck!