Date: Erev Pesach 5585
From: Rabbi Moshe Sofer
To: Rabbi Yaakov
The Chasam Sofer rules that meat between the 12th and 13th ribs is permissible in communities like Pressburg where hindquarters are sold to non-Jews, since the regular butchers handle all the ribs and are experienced in the light nikur required there. He distinguishes this from the warnings of the Zevach Shmuel and R' Shmuel Landau, which applied only to communities with separate expert nikur workers for the hindquarters, and criticizes the Ohel Yitzchak for applying Prague's standard to Paksh without recognizing this distinction.
Source: Shu"t Chasam Sofer YD §68