@aviradearah. You are right. Rabbi Wolpo wrote two books. One: the above mentioned Yechi Hamelech which discusses Moshiach in general. Two: a book called Yechi Hamelech Hamoshiach which discusses the Rebbe having a chezkas Moshiach. It has haskamos from Rav Ovadia, Rav Mordechai Eliyahu, Rav Hirshprung and Rav Moshe Stern among others.
