Ian/Jesper/Remi - Isonic 115 & Fins

[Daniel B]

Hi guys,
A month ago I bought an Isonic 115 and I am really happy with it.
But I would like to add some lightwind and upwind power, so I am thinking of buying another fin ( I only use it with 8.0 V8 and weigh 75 kgs ).
When the wind is really light ( 11-12 knts ) I find it hard to go upwind.
I know this board is designed for slalom racing, so adding fin will create more drag and reduce speed, but for "allround" sailing ( I mean not racing ) I am thinking of buying one fin in the 44-46 cm range.
1- What do you think ?

Regarding the brand of the fin, I have a chance to buy a Tectonics Spitfire 44 or 46.
2- Do you think is a good fin for the board ?
3- Are the tectonics more powerfull than the curtis ? If this is the case, I think I would go for 44, if not maybe 46. Right ?

Thanks in advance
Daniel