Best fin for isonic 101

[steph97200]

Hi Kevin,

I have the isonic 101 (2009 model) with a NP RS Racing 7.2m².
This sail is my only sail for this board.
I mostly use this combo from 13 to 20 knots in choppy conditions.
My weight is 66 kg for 1.78m.

I need your help for the choice of the best fin(s) for this combo :
- Deboichet SL2 or SL4 ?
- 36, 38 or 40 ?

Is it useful to have one fin for high wind and another one for light wind if I always use the same sail (NP RS Racing 7.2) ?
What would be your suggestions for the model and sizes of fins ?
Thanks a lot for your time.....