Roman Shades are manufactured in standard pieces of 2 ft. Thus, the length is a multiple of 2. The longer the Roman, the bigger the drop loop (see picture)
The maximum width is 8ft 8inches. Measuring from the inside face of the beam: Roman Width = Pergola Width - 2 inches for clearance
If your pergola is wider, you can simply run 2 systems side-by-side. We recommend a 1-inch clearance between each Roman Shade.