My tracks from the early days are rather tame next to these monsters. Below, for instance, is the eternal classic - according to the hilarity shared with my "team mate" when we were nine years old
The only good example of a track designed for sheer insanity is the following design, done by six hands a few years later. It might well be possible to do it in less than 4 minutes without shortcuts...
Honourable mention to Nuova, which I designed just after getting the idea of the fake track gimmick from Luke's site.
The A-4 track in stuntschallenge.net is from the same era of the latter two; that is a reasonably sane design though.
(Tracks attached below, should they fit your fancy)
