I am trying to remember if was a Scamp that I saw where they built a bunk but it seems like it.  I remember that the setup looks a lot like the bunks that Parkliner does.  Have you seen the ones in the Parkliner as that might give you an idea if you haven't seen them.  I am going to try to find the one I saw where bunks was added but I look at so many photos, I might not find it.  I have seen the rare Casita with the side bunks a couple of times.  If I come across it, I'll get the link to you.