Please help me understand ds?

Measure across the entire length you want the ds to fit and that will tell you how wide they will have to be in order to draw closed. Since this isn't a standard width, you will need a custom d. If your sister is familiar with sewing dries, she could do it. Otherwise, this is a custom order. Ds have to be pinch pleated, lined and hemmed. You definitely would not want pocket or tab tops for a d that has to draw. You will be tugging at them and on your rod constantly. So a grommet with a hook to fit into the pinch is highly recommended.