From: Rabbi Moshe Sofer
To: Rabbi Yechezkel Segal
The Chasam Sofer rules that 'Hershel' is a diminutive of 'Hirsh' and should be written as 'Tzvi, known as Hershel' without a yud; if a father's name spelling is in dispute between Yeshayah and Yeshayahu, the husband's testimony is credited, or two gittin are given with the shorter form primary. He further rules that the mother's name may not replace the father's name in a get except for a shtuki or asufi, and that compound names like 'Refael Leib' follow the formula of 'd'miskarei Refael Yehudah' per the Noda BiYehudah.
Source: Shu"t Chasam Sofer EH II §25