balancing/finishing work

Question
Hi, I am looking for some good exercises to do with my Arab gelding, he will be shown huntseat.  He is coming along very well, he just needs some finishing (better upward transitions, more balance at the canter).  I'd like to find some exercises I could do with him to help him along, especially at the canter. He is a bit strung out and has occasional trouble with his leads.  

I once did a clinic with a different horse with a dressage trainer and she suggested doing spirals-cantering a wide circle, making it smaller, then wider again.  This has been a great technique and I'm looking for more things like this to do.  

Thanks for any input.

Answer
Dear Mel:
The excercise you describe is basically a leg yield on the circle - it can be done at all gaits - so although you describe the canter as being your horse's achille's heel, it is a good one to practice at the walk and the trot also. In addition, using your arena's long walls and the quarter line (the "invisible" line half way between the rail and the centre line) can help. Begin at the trot coming off of the short wall- go into a leg yield toward the quarter line, straighten out for four strides and leg yield back to the rail. At the canter, same thing- make sure to hold the bend- supporting with your outside rein- especially as you leg yield back- making sure your leg is at the girth, not behind it, or your horse may think you are asking for a change.
Another good one is the serpentine. Coming off your short wall, begin a twenty meter circle, as you approach the centre line, do a down transition to trot. Set your horse up and get him balanced for a transition to the opposite lead and begin a second half circle. Three of these should take you end to end in your arena (think about riding the shape of the letter "s" with one extra "loop." As your horse accepts this, instead of coming down to trot, come all the way down to walk, gradually shortening the number of strides at the walk to one stride. Changes on the centre line are also good for helping horses who may tend to support the wall or track crooked.
Best wishes,
S. Evans