Back-reference in *Gal 5:21 and its implications for Marcion's Gospel and his Pauline Letter Collection

A crucial discovery information is given in: *Gal 5:21 ("as I said before"). This small sentence provides us with a back-reference. 

If I am not mistaken, it can only refer to *1 Cor 15:50. This clarifies one of my uncertainties whether or not the redactor had written or oral material in front of him, when putting together the collection of 10 Pauline letters, credited to Marcion. 

A back-reference only makes sense, if the letter with the back-reference, is part of the collection. As it goes into the wrong direction within the 10-letter-collection of Marcion, this reference must be older, unless Epiphanius where we find this, has given us the canonical text and not the precanonical one.

On the basis that he gives us the precanonical text, the redactor must have used an older collection of 7 Pauline letters plus a collection of the 3 Deuteropaulines that have already been identified as a collection - see their position in the collection and also their lexical and semantic and content proximity). A back-reference that is incorrect in *Gal 5,21, hence, shows us this and several other things:

1. This earlier collection must have had the order *1Cor - *Gal, hence most likely corresponded to the canonical order of Rom - 1 Cor - 2 Cor - Gal ...

2. This collection, though of canonical order did not derive from the "canonical" camp as do the *3 deuteropaulines.

3. The redactor is of a rather conservative type. Though he reorders the letters, because the new order supports one of his main positions, the strong statement in *Gal 1:1 with regards Paul and the antithesis between law and belief, but he leaves the back-reference, so does not hide the fact that he is using an older collection of a different order.

4. If this redactor has only made use of already existing written collections of Pauline letters, it is most likely that he also made use of written material, already collected in a certain form for *Ev.