Just happened to stumble across this old thread. The Horseman LE came with a 400mm fixed length monorail, while the LS and higher models came with a 460-700mm expandable monorail. The LE also did not have Base Tilt, while Base Tilt was available on the LS and higher models.
Originally Posted by Arvay
The optional short rail for all cameras was 250mm, and there was a 1000mm rail option as well.