I used to trace pictures of horses when I was a kid
Try to find a picture in a magazine or book at the angle this horse is in, then try to draw the legs to match. It's easier if you can find one in a similar size, and draw it on a thin enough paper so you can see the picture underneath and trace. Make sense?
I would look at jumping photos on google and see what the horse is doing. For example of he's jumping down over an embankment into water be will look different than if he's jumping an oxer. Study what real horses and riders are doing in photos then translate it into your drawing. Posted via Mobile Device
That's a good start. Its a difficult perspective, but you are doing well, so far.
I use a pencil to help me determine the size ratios of things to each other. Sometimes we THINK something is bigger than something else, so we have trouble ptting them into perspective correctly. But if you use a pencil, up against the screen, and measure, like this:
The distance between the rider's elbows is the same as . . . . And use the pencil and find soemthing on there that is the same, and then draw them the same.
Or, the distance between the pupils of the eyes (on close ups) is twice the distance from the pupil midline to the nose.
You compare one known thing to another, and thus you keep the relations accurate.