My first bargello was Ribbons in Motion, and since the strips didn't go to the full top and bottom, but had background fabric attached, the tube method didn't apply.
If I were doing a "first" bargello again, I would stick to the directions, and tape them to the wall so they don't go missing or get upside down.
Once comfortable with the technique, then go ahead and change things up to suit your style of sewing/quilting.
IMHO