Great news Denis. Nothing is more fun than hearing success stories.
Agree on the pre-bend issue, sounds like you need substantially more pre-bend. I would have talked with the guys at NACRA about how much bend you can put in the mast safely, then found a combination of spreader rake and diamond tension that matched the sail and your conditions well.
I tried trough the site search engine to find out more about mast and sail tuning but I had a hard time to get good result. Any clue how to refine my search? I would really like to read about the subject.
I can not help you with any articles on pre-bend and sail setting. That topic is quite dependent on your equipment. In your case where you try to match your mast to your sail it is a matter of trying several settings and tuning for best performance to your conditions, boat and skills. When you can make all telltales fly in all wind conditions, you are getting close in my opinion. Then start finetuning for your best performance in your dominant conditions.
There is a lot of NACRA experience here and they can probably give you good advice on how far you can go with spreader rake and diamond tension. Is your mainsail a standard NACRA20 main?
