Some of the reasons that draperies recommend dry cleaning is not the surface fabric but the combination of elements in draperies. Lining is frequently treated with all sorts of chemicals to provide warmth or sun protection. The header tape is made of buckram and will shrink and pleats not return to the normal look. Sometimes the finish on the face fabric has special finishes to give sheen, etc. So after deconstructing the panel, wash all or part of it and see how it behaves. Sun damage or light damage will quickly show up. I have used a lot of drapery fabric in quilts in years gone by because I used to do drapery fabrication as a business.