Two things to keep in mind:
1) The word "plans" probably doesn't apply here. While working on my 5er I've found that surfaces that look square or parallel to each other often are not, and even the curves at the front of the 16' section of the trailer (where it connects to the loft) are not the same on each side. Add that to the fact that no trailer-side-surface is flat or straight or vertical, that wood-to-fiberglass connections have to consider the fragility of the
fiberglass itself and you have a woodworking challenge on your hands. So, even if I did keep "plans" for my modification, my mods probably wouldn't work in your trailer. You'd have to make changes so all the surfaces mate up with each other. With these things in mind I'd say this is an "advanced" skills project or perhaps an "intermediate" skill project for someone with a lot of patience.
2) And my plans probably wouldn't meet your wants and needs. Mike and Nancy's trailer, which is where we got our basic idea from, is very nice, but not what we wanted. Our mods probably wouldn't match up with other people's needs either. The nice thing about doing your own customizations is you get to create the kind of space you want, not what someone else wants for you.
--Peter