@haddock: Sure, you can post teasers. Also, trenches may be up to 5 feet deep and 10 feet wide, to allow the track spine of very low to the ground track to clear the ground. However, water is not allowed, and neither is any raising of terrain.
@gazag: Any point at which the track is banked more than 155 degrees relative to the banking at which the train leaves the station (0 or 180 degrees, depending on whether you're building a Vekmoma or a B&M), is considered an inversion. Example: If the track contains a lie-to-fly, and then a fly-to-lie, with no other inversions, it will be considered to have one inversion.