i have had horrible luck with urethane tranny mounts, tore them in my street bug, tore them in my scirocco
went solid mounts in the street bug and they held up, if you dont mind the noise..in the scirocco,went with german rubber with a higher than stock durometer rating and love them.
not sure about the air cooled mounts, but all rubber mounts are not created equal, some of the india/china/mexico mounts for the water cooled cars are like black jello