That sound interesting, we don't have a stone issue with our own beet but some I buy in from elsewhere can have stone problems. Have you any pics of your conversion? We had Standen Sceptre harvesters back in the 80's and their cleaner unit comprised of four contra rotating cleaning barrels with retractable 16mm steel rods. There were also two oscillating smaller rollers between them to keep thing moving. It was an amazing design that took out all stones, clods and trash very effectively indeed and was also gentle on the beet. In fact it would block rather than let anything through prompting you to go slower. Down side was, it was expensive to run with steel rods and slots wearing rapidly. I often thought how good this type of design would be in a cleaner loader.