I cooked one of these unrolled and it seemed to dry out. No one really liked it so I am nervous to do it again.
From my friend at Texas A&M: "Chuck Flat is a bit of an issue and a question I get from time to time. I think what they are talking about is the chuck flap, which is the portion of the chuck roll that might be referred to as the tail. If that is what they are selling, it is the Serratus Ventralis muscle, which is the major muscle in chuck short ribs and plate short ribs. It would surely do to either slow smoke to about 190ºF like beef short ribs and should be really good, or you can braise. It will look good enough to steak, but they are always tougher than i would like."
So anyway I smoked them until 190 and thought they were dry. I didn't wrap or do anything really. I miss my beef ribs!