Menachem Mendel notes that the archives of a short-lived journal called S'vara are available here.
Volume 2.2 (1991) contains a symposium called "Prozbul: Was Hillel True to Tradition?" containing Prozbul and Legal Fiction by Pinchas Shiffman, Prozbul and Rabbinic Power by David Kraemer and Prozbul and Poseq by David M. Gordis. (link). I haven't read it, but it's an interesting idea for discussion.