At my first ever tourney in 2003, I entered the beginners div at my weight. In my first fight, I was thrown, mounted and submitted in about 10 seconds (no exaggeration). I was stunned. No one at my school had ever just completely destroyed me like that. I was in the locker room trying to gather myself, and a teammate ran in and told me the officials were looking for me. Someone watching the fight knew that my opponent was a Black Belt in Judo, and told the officials. NAGA disqualified him for sand-bagging, and awarded me the match. I went on to take gold and receive my Blue Belt because of how I performed in that tournament. So, speaking from personal experience, if you have a Black Belt in Judo, you have absolutely no business in the White Belt/Novice division of a BJJ/Sub wrestling tourney.
Great story, and way to go, picking yourself up and winning afterwards.