Cheryl, I have made one bargello where I had to use the tube method, but I'm not fond of it.
The bargellos I showed in the tutorial have a certain number of fabrics showing at the top of the quilt...I'll say seven. A color goes down seven steps and them back up to the top. And that repeats across the width of the quilt. So if you are going to need strata with only seven different fabrics on the top, I feel that is better to sew those and when you cut then into the widths you need, it saves all that snipping out and resewing. I really have a hard time snipping out a seam at the currect place. Even if I open the tube in the currect place I've been known to sew that strip up side down.