Would say its better to be underpowered when learning than overpowered?! i know an experianced rider VERY similar to your weight that gets going in about 15mph and up past 30 on his 11, 2m may not sound like alot but it is
Propper use of the trimmer helps alot. In light wind i will trim a couple of cm, to increase the speed of the kite, this reduces the power, yet increases the speed helping to increase momentum. As the wind builds i'll trim out again for full power and optimum flying. Then once the kite is getting over powered i'll trim in again.
I guess what i'm trying to say is, use the trimmer, and not just for being overpowerd. Good understanding of this will give you the maximum wind range and fun.
If you feel overerpowerd use it. When it's light, and if you feel the kite stalls when you have the bar all the way in trim it.
The trimmer is there for a reason to trim you kite for the conditions.
Use it, and you'll have a lot more fun and a bigger windrange:D
Like Marman say's when learning your better under than over powered.
So pull on ya trimmer.