I would like to clear up a misconception.
CDE is NOT NOT NOT about speed.
There is the dressage phase, which is just like ridden dressage only with a cart. No speed.
There is the marathon course. You have a minimum and maximum time to do it in, so again, not about speed persay, if you go too fast there are penalties!
Then the cones course, there is a max time you need to be under to be free of penalties, but since it's about flowing through the course without knocking balls, again, it's not about speed!