I think I might experiment with a Keep Going Signal (KGS). Someone wrote a response to the blog on a list I am on and asked why I wasn't using one. She explained how she uses it with duration behaviors such as going over trotting poles and also for something in a series of behaviors like a canter depart or flying change. The reason for using it with going over fences or a flying change is that you don't want the horse to slam on the brakes when he hears the click. Many times that is acceptable because you then can ask again, giving the horse several repetitions of successful behavior. But slamming on the brakes when landing from a jump is not good for the structure or performance...so a KGS would mean "good job but keep cantering until I ask you to stop or you hear a click".
To use it to keep the trot going, I would first condition a KGS by using it right before the click and primary reinforcer (treat). Ande would then learn that the KGS (I'm thinking of using the verbal "gooooood" which just kind of oozes out of me when a horse is trying hard) means that a click and treat is coming and he needs to continue what he is doing to get it. That is why it's called a "keep going" signal. Rather than getting frustrated and quit because he isn't reinforced, he would know to keep trying.
I looked up KGS on Karen Pryor's website and this is what it said:
A signal, verbal or otherwise, given in the middle of a behavior to tell the dog he is doing the behavior correctly and should keep doing what he’s doing. Keep-going signals add an unnecessary level of complexity in training.
So, obviously some consider KGS to be unnecessary and complicating. I think the reasoning is that simply withholding the click has the same affect. Has anyone else experimented with them and found them to be helpful or complicating?