Yes, the stay fits in as an upside-down U. I use Velcro tabs on a lightweight flap to cover the upper, cross-bar, end and to hold it in place. The sleeves are 2" wide by about 20" long strips of coated rip stop that are folded into a tube and sewn into the seam that joins the side panel to the back panel (closest to your back). The stay is placed on the piece nearest your back and the pad sort of fits between the side rails.
Pictures of the stay installation would be tough since it is almost all inside the pad pocket. I'd be happy to share photos of what I can photograph including the upper part of the stay assembly. PM me your email address and I'll dig out my camera.
May I walk in beauty.