Hi F.A.
As I was posting the last message, 'Chumpy' came into the shop & described the conditions that your situation occured in.
(Bring your sail in, we'll sort it out,maybe we'll even find you a 2nd hand (carbon) boom)
Young Chumpy was saying that he was a tad overpowered sometimes with a 7.0. & he's no sparrow,( no comments on Christmas turkeys) so it's hardly suprising that you were coming across a few problems.
Grumpy would be right for some situations, though from what I hear for that day, the rollercoaster would have been even worse with a bigger fin.
My viewpoint comes not from my ego, nor casual observation but from 20 years of an an instructors viewpoint.
The main antidote is experience, but the fun of the sport is getting that experience.
The path is lined with pain & payment(usually both) but it's fun

Have fun.
Jez www.2ndwind.com.au