I feel quite often that I would love to write such a letter,but I also feel that it gives them the chance to put closure on their feelings.
They don't like it when you have left for conscientious reasons and are still free to express these reasons to those still in the cult,you present a danger.
I would rather continue to be Mr. Dangerous and make them feel uncomfortable for a lot longer yet.
Whatever you decide to do,good luck and all the best for your futures,and please keep posting.
Love
Wobble