Well, I'm impressed not only with your dedication to finding out exactly what your horse is doing, but also with your 'non-technical' terms... which I understood perfectly! We must use the same kind of 'non-technical' dialect!
So, if your horse is rough when you are sitting as the left front hits the ground, the short answer is that you need to keep working on this side... that is, keep sitting on that diagonal, as this will build up his strength. Could you feel that as this became more uncomfortable the horse was trying to get you to change over to the right side?? Often riders will change when they feel this uncomfortable stride, however that does no favours for the horse.
Keep up the great work!!!
My buddy Duncan McLaughlin also has this to offer:
"Tell Don this:
1. his diagonal where he posts higher might well have more to do with him than the horse; and
2. If he wants to know his horse's weaker diagonal he can look at its front feet. The smaller front foot belongs to the less weight bearing diagonal and he should sit on this diagonal more."
