I know next to nothing about NATRC, but I condition all the time with a group of very experienced endurance riders and none of them stand in their stirrups to trot. There is one exception and that's when going up a very steep slope. Most riders rise when climbing and there's one spot that is so close to vertical that I am actually standing in my stirrups with my hands wrapped in Hunter's mane as he rises ahead of me.
There are, however, endurance riders who adopt your friend's "hovering" position. I can't really imagine riding very far that way. We all post to the trot. It is easy to learn to do and probably easier on your horse's back going over a distance. You may need to shorten your stirrups a little. Let the propulsion of your horse slide you forward as you rise and ease you back as you slide back into the seat. Someone else probably could explain that a lot better. Nancy
