Hi,
I am 30 yo, 82 kg, learning to windsurf in Canaries, Fuerteventura. We have strong winds most of the time. Rarely do we have less than 20kt (unless it's winter here).. So far I am renting only. So I can pick any equipment I need.
I am currently windsurfing 150 L fanatic shark board. I can get it to plane, and if conditions are nice (offshore wind, flat water), I can get my front foot into the strap. Not a back foot though yet.
Now the struggle I am currently experiencing is, when the wind picks up and/or changes direction, we have some swell rolling in, together with nasty chop.
So for example, my very typical "sux" session was yesterday: wind ~18-20kt, with gusts up to 27 kt. Swell rolling in + choppy. And I was with 5.6 m2 sail and 150 L fanatic shark.
The moment I turn downwind in the gust, to get planing, it seems like I am driving a jeep at 90 km/h offroad. Everything's just bashing, I can barely stay in control, and only for a little while... I am basically fighting the elements and after ~50 minutes it's usually enough and I am getting back onshore..
Now after reading through the forums, I kinda am getting an idea I need to get onto the smaller boards.. Would that settle things down a bit?
I cannot waterstart yet..
Sometimes I think that those learning in lakes with not too much wind have it easier..
It sounds like challenging conditions for a beginner. However the windy conditions will be better for you in the long run. First thing to do is learn to waterstart. Once done you need to look at getting a smaller board, something around 100 litres. You will still be able to uphaul this board if the wind drops away together. The smaller boards will be more manageable in choppy conditions for you.
If it is the board to blame, and not my skills (ha-ha), I assume I should downsize asap, at least to 135 then.. even without my waterstart skills ..
smaller board will be easier to control in chop and strong wind, if you can rent start with something around 130 lts and go down, but for the chop get one that is not too wide, max. 75 cms. Also work on getting the 2nd foot in the straps asap, will give you a lot more control. And if it's too windy send some over here please 
Yep, you need a smaller board. I'd try the 135 and then keep trying smaller. 18-20 knots, I'd be aiming at 90-100 litre. You will struggle to up-haul this especially in choppy water so water-starting practice is a must.
By the way, if you are sending some wind over I'll have a bit too. Bloody Winter.
I can recommend the Patrik 125L Freeride. It's a little longer and narrower than many boards of that volume. It is very controllable in messy chop and fine in strong wind. You can up haul on it. I've used it with a Crossover 5.6m in 20-25kts with short, steep chop and it put a big smile on my dial. It would be a good step down from the 150 Shark. Later when you have gybes and waterstarts nailed you can go for a 90ish FSW and then you;ve got everything covered 
