I'd seen this done most often with two engine stands, and pine 2"x8"s, or two engine stands and some fab work using 1" square pipe.
We set up a rotisserie to work on a friends race car this way (with the 2"x8"s) and it worked Ok, but wasn't what I'd call a sturdy structure. It did keep the uni-body off the ground, and with 4 people, we could flip the body upside down.
Attachment points on a Beetle would be the issue though. Maybe with a 16 foot joint of schedule 40 pipe passing through the windshield opening, back through the rear window opening, and braced into place with some 2"x4" truss work in both the front, and rear window openings, and an engine stand on both ends would be suitable. I'd never tried it like that, but that's 'bout the best home-grown VW rotisserie aparatus I can visualize.
