I suspect that your plant is not yet mature enough. I checked for plant size descriptions of the 6 awarded Mark Hasegawa's that I could find in the AOS database, Only one was to a single growth plant. There was one from Krull-Smith that had a culture award. The plant had 5 growths measuring 22cm. long in an 18cm. pot. What is 18cm., about 7 or 8 inches? Your plant is but a single growth in what appears to be a smaller pot then 18cm. You just need a little patience and let it grown up. Good roots are a plus for sure, however roots are just part of the overall picture. Another award went to a single growth plant with the growth measuring 29.5 cm. wide. That is close to 12". Another award mentions a several growth plant with a 35cm. wide leaf span. You need to get this plant to mature a bit more, getting some "oomph" behind it!
