Bummer! I really didn't want to cut it out, and was hoping to have the hollowed out area for extra insulation space.
Here's a photo of the edge that appears to be folded over (interior panel, btw)
Grrr... Now I can't decide if I want to give up that space or not.
My impatient, "damn I'm broke" side says just leave the silly booger in place, add a layer of insulation over it and get on with the build!
My practical, "long-term-view" side says take the time to cut it out and insulate properly - I'll be living in the space and will be happy I took the time to add extra insulation later!
I think next time I'm out at the bus I'll take another look under the panel and see just how MUCH fiberglass insulation is under there. If there's enough of a layer, I may go ahead and leave the panel in place, build over top of it, and figure out another way to cover the windows later.