I (at 100 kg+) use a similarly sized board, the Exo Cross 106, and use a 30 cm upright fin with a 7 m2 sail. works fine. But for absolute low end performance I have actually used a 40 cm fin as the Cross has a Powerbox. But generally the 30 cm fin is a much better fit (and a 26 cm wavestyle fin for 6.2 and smaller).
Go for it.