There is no "official" info.
A few years ago, a buddy of mine wrote to Porsche asking about head temps in his 2.0 914 engine. They wrote back, "Ask VW--it's their engine."
So he wrote to VW. They responded, "We don't know--we never found it to be an issue."
I'm guessing that they simply tossed out all their aircooled data.....
--DD