Hi Dani
Izymiester is right with the fin size of 42cm (Canefire) for this board.
Don't be to scared of the size as those fins handle a lot of wind and still keeps the board in control.
Spin outs can easily come from a fin that is to small,,
I haven't tried the C3 fins , so I can't comment on those,,
I can see you are from US, so just send Jeff Fagerholm (Vector fins) a email there and he can help you out.
[email protected]Cheers
Jesper