Add at least 4" to face width and 2" to returns of any under-treatment, e.g. sheers, for proper clearance.
Stripes and plaids are not suitable. Sheer fabrics are not suitable.
The cascades and the flat underlay should be constructed of the same fabric.
An accent fabric can be added as the contrasting cascade lining and possibly the welt at the hem of the flat underlay.
This window treatment cannot be inside mounted because of the gathered cascade bulk at the top of the board.