Czech TV report:
http://www.ceskatelevize.cz/ivysilani/210471290650001-motocyklove-zavody/
Mr Snackette is right - rider #7 can substitute any of the 1 to 4 riders at any time. However with the maximum of 5 heats (not including final heat).
Rider #5 could be replaced with junior rider only.
Final heats:
Heat no. 14 - 3rd and 4th best riders (including #7) of both teams after heat 13 (could be replaced with #7, tactical reserve or JOKER)
Heat no. 15 - 1st and 2nd best riders (including #7) of both teams after heat 13 (could be replaced with #7, tactical reserve or JOKER)
