Indeed a two person job. I made a wooden support frame to be used on top of the transverse bars. This way the Bullitt is positioned closer to the roof (compared with a Thule style bike rack), makes lifting it in the roof a lot easier.
Made a cut out for the steering rod using a chisel, the bike is supported underneath the cargo area.
Have used it for a cycling trip in France, we drove more than 700 km with the cargo bike on the roof before we started cycling.