Schmid has proven convincingly that Epiphanius used Marcion's texts (Marcion, 173), in contrast to Clabeaux, who thought that Epiphanius did not but rather used previous anti-Marcionite works (Lost Edition, 14).
I am not sure I remember this comprehensive argument. I always hate it when scholars just say 'someone else proved it.' I don't remember Schmid 'convincingly proving' this assertion. Wishful thinking I suspect because I came to Clabeaux's conclusion a long time ago. Do you ever get the feeling you are just too honest to be engaged in the business of scholarship? What if the real bottom line is that we can't prove anything and our fate as a culture is just to move rocks from one pile to another all day, every day for the rest of time?