I would say that my matrix (linked to above) is a good starting place. I went 4' past the back bumper and tapered it to the size I wanted the back to be ~15 degrees. I also used a large piece of Plexiglas to keep my rear visibility.
I think your idea of a bike rack might work, or just buy a hitch for the car and use that (which is what I did).
I am happy to answer questions if needed
