I see... then yes, the sheetmetal version will probably work best for you.
I cannot seem to modify the 2 flatten quilts in my Creo 2.0 as you have them defined.
Is this a Creo 3.0 file or WF5/Elements Pro? It opens in Creo 2.0.
I have noticed that flatten quilt builds a "plane" from the edge at or near the point used in the flatten quilt. If it is a good straight edge, it does pretty well. In the case of the fill/boundary blends, however, it takes some serious liberties with the tangent merge along the two surfaces.
Have you considered just forming a round tube with a square die 
The attached file is working pretty well. Is the same as the previous with the garbage removed and to re-forming.