It would be very difficult for an athlete to hit a BMI over 30, for most it would be impossible to carry that amount of lean mass.. without pharmaceutical help that is.
It depends on the person. I am 5'5 and and I would have to be about 175 to get under 30. In high school, I was 5'4 235lb and in ridiculous shape. Granted half my family are huge barrel chested short guys w/ legs like tree trunks. 18.5 inch neck and 34inch waist and 14-15% body fat. I had some friends in similar shape like you who were taller and their BMI was always low. According to BMI (40.3), I was Obese Class III (Very severely obese). Never touched steroids and barely lifted at the time. The chart severely skews shorter athletes to taller.