[addicted2sp33d]

I don't know about older Beetles, but here is our Tandem on my wife's Beetle.
No special mounting equipment, just the OEM Roof bars and some ratcheting straps.

It's completely steady up to 70mph. It's probably stable above 70mph but the kayak basically doubles the wind resistance so I haven't taken it above 70mph.

For reference, the yak is a Pelican 130T (13' length, 36" beam). The car is only 1' longer than the yak!