Brass weight spinner nuts from MECOA could be a solution if your spinner cone is of the type that allows it. Those spinner nuts come in different weights and thread sizes. ISport is a good-looking plane.
Like my Escapade 61, it too turned out tail heavy with the recommended engine size. I went with a larger OS 95AX, but then found that the landing gear was too short for the 15” prop. So then, I spent more money solving the issue with a taller landing gear. What’s with these designers?