Yes, write a letter to disassociate yourself. That way when they announce your name at the meetings it will
give the impression that you left on your own free-will and not because you committed some horrible sin. Not
that it really matters since you'll be shunned and treated as if you were lower than dirt, but that's okay since
you only have to consider the source. When they say, "(name) is no longer a Jehovah's Witness." - people
will be wondering why you would leave "God's loving organization" ... maybe it will give others strength to do
the same. I'm sure there will be those who will be thinking, "Lucky guy! Wish I could leave too!"
If you need help with the letter, PM me.
Good luck!