If it is going to be hung instead of being on a bed or table, why does it need a binding? If it is a case of wanting the confetti pieces to stick straight up at the top, instead of bending over due to weight, I might blind attach them to the sleeve. Otherwise, I think I would carefully cut away the excess backing and leave well enough alone.
It is beautiful Watson. I know that a lot of anger and grief and tears went into its making. I am glad that smiles and sunshine made their way in too.