After mulling it over, I have decided to try to get access to a round pen in order to work him at the canter more on the ground and then to work him at the canter under saddle without having to worry about steering around trees and trying to avoid downhills. Once we have it more solid and he is more comfortable responding to cues, we will shift back to the field again.
He has only recently started cantering on the lunge line. He was too fat and I was too pregnant when we first started training.
It is always better to have canter work down right from the beginning. It has been interesting training a horse without the ability to do it by the book.
Tomorrow we will see how ride 3 with canter work goes!