Okay, I don't stitch the reverse pleat down until after I've sewn and tacked down the pleats and the fell. That allows me to get a better idea of how to align the pleat and the overapron. As for those 11", they turn into the reverse pleat, since you'll align the edge of your overapron next to the edge of your first pleat, creating a fold beneath the over apron.

Also, I don't put the velcro on until after that's all done and I'm ready to put the waistband on. That way I don't have to worry about all that stuff. I had to learn this after making my first x-kilt. So, you might want to take off the fabric with the velcro until later.