5-4 in Sweden? I used to be on 3-2 in Norway
I'm no expert on Sardinia having been there once. I loved the place, but seems to me that the wind down south (Trettu) is nothing close to what it is advertised to be. We had wind for 50% of the days or something (in June) and I think I was on my 12 once and used the 17 for the rest. Obviously anecdotal, but this idea that the wind is 5 knots higher than the forecast (or whatever they say on their homepage) certainly wasn't true when I was there.
That said I wouldn't mind going back. I really liked Calasetta. Very nice quiet little village.
The spot is decent. Restaurant is extremely slow, but who cares kind of thing. Nothing really happens in the area of the spot other than kiting. When it is not crowded it is sweet flat water and if the wind dies you can just walk back (the flat part is off shore when the wind blows from the north) because it is so shallow. When crowded it is slightly more tricky as it is fairly straight off shore meaning you often get stuck behind someone close to the "beach". Especially in marginal wind when people don't really want to go too far down for the risk of not getting back. In strong winds you can go far and because the water is so flat it is very easy to get back even if you are not every experienced.
I would like to go back some day, but not purely for kiting. It would have to be a romantic holiday or something in one of those villages. Maybe combine it with cycling. But for that Sicily actually looks better.