As Decoration
Sometimes you just do not need a Ribbon pleat you can use a normal pleat. If you are not going to curve your pleats and you only are going to have them on a straight line you can use less fabric or ribbon by using normal knife pleats. With this hat below (from my 1870-90s Victorian bonnet pattern. I used a normal pleater board with 1/2″ pleats.
Each color was pleated separately then sewn together down the center with two lines of stitching. Each color was a a strip with the edges folded and pressed into the center along the longways. Each one was wider than the other going down to the turquoise. This is a view from the right and the pleats go up.
When you look at it from the left side the pleats go down. The end of each side has to be treated a little differently. They are tack together where they meet along the bottom edge..
As a Crown Covering
This Victorian Brimless hat was covered with 1/2″ knife pleated silk taffeta. The edge of the pleated fabric goes down to the head opening and the raw edge is covered with silk bias tape.