Double words - is is, had had, that that – are they correct?

Quando o texto requer uma palavra repetida acabo reescrevendo a frase porque, como muitos dos meus clientes tem um conhecimento  limitado do idioma, iriam certamente achar que era um erro e possivelmente eliminar a palavra repetida.
                    Exemplos de construções corretas:
had had
      If I had had the opportunities that you had I wouldn't have done what you did.
      She would have traveled around the world if she had had more money.
      We had had that car for ten years before it broke down
is is
      There is nothing between them and trying to imply there is is simply wishful thinking.
      Exactly how long a stadia is is unknown.
      Everything that is, is because other things are.
that that
      I know that that is not easy to understand.
      That that should be me is unbelievable.
      What you have to accept is that that talk exists in the community.
      I'm glad and sad that that's over.
      I know that that school is that famous because of its rules.