Yes the triangular kasan is necessary. Leaving it flat will only result in a lot of extra weight on a non bending part = poor performance.
How did you try to string it?
First step is an a stick (asi gezi) to go between the tips. This will allow you to see any twist and correct it. Then you must go onto using tepliks. Again these allow you to see any problems before stringing it. The bow must look perfect before you try to string it.
The deal with collagen glues is that they get stronger and stronger as time passes and it not just about moisture leaving the bow. The longer 'drying' times are definitely worth it as the bow will be harder to overheat and will be more resistant to twist.
I understand what you are saying about how you learn and all that but that will be a very,very long road for you! Composites can have many,many things go wrong......however if you do things the traditional way then you start finding that things don't go wrong anymore!
If you want advice on anything just ask. I think i've finally got a bit of a grasp on making these bows.
I live in England.....man I would love to live in a dry climate!
Do you have Adam Karpozwi book?