Well standard practice over here is to have a crane mounted on your trailer to lift up the mast and set it on the base.
That would be a an impressive trailer

Anyway, I rig on the trailer and stand on the tramp supporting my 13kg, 8.5metre, mast as I figure that my weight plus the mast has got to be less then two sailors on the tramp if the boat was two up, my boat also has the advantage of a fore and aft centre beam. The boat is supported by the main beams, not the hulls when on the trailer so no harm is done. I also rig up fast, contrary to other advice, I can do it in 20 minutes from arrival to hitting the water, as I do it a couple of times a week and I'm there to sail, not stuff around.
I have noted that some sailors of various classes seem to prefer rigging and unrigging to sailing as they spend hours and hours at it then nip out for a half hour sail. Strange behaviour

Darryn