I put one of the booms on the fus and then attached the tail, when you try to line up the other boom the gap normally is at the front of one of the booms, at least it was with mine and elongating one of the holes for the ali pins cured it, I don't think the tail can be too wide as its made in a jig as far as I know, if you are still having problems contact Partricia at Boomerang jets, she will sort it out for you if you need a new part.
Mike