How do I get my Isonic 125 faster..

[Hookipa18]

So far my to speed has been 55.2 km/h combining the Isonic with a CR 7.7. Used the 44 fin that time as the wind was gusty and on the lighter end for a 7.7.

Did 51.6 with the 9.0 combined with the 44 fin yesterday. Think that is not too bad for the size sail...

Compared to the light wind set-up the speed I'm getting out of the 7.7 dissapoints me. Next time I will use the 36 stock fin. But the board doesn't feel loose when I sail with the 7.7 (fin?)..

I have the mast pretty much back in the lower half of the mastrail.

All tips apreciated.