That's what I thought, that's why I asked if it is floating. The reason I was asking if it floats is that you probably don't want to build a wall on top of it. I thought you already had the pergo installed, guess I was looking at the wrong thread.
My bus has the roof (outer skin) and the ceiling (inner skin) with about a 3" space filled with fiberglass insulation between, I think most of them are built this way. I secured studs to the ceiling using toggle bolts. I didn't have a problem accidentally going through the roof when I drilled the holes for the toggle bolts. In places where I didn't want a stud wall, but I wanted a vertical piece of plywood as a wall, I used brackets and sheet metal screws.
Those are actually chair corners, a little fancier than el brackets. You could do something like this all the way around the divider, position the divider whar a window stanchion is and use brackets on the floor, up the side and on the ceiling.