This added weight can put the horse off balace and make it even harder to have a nice jump over a fence. Now, in hunters jumping the fences shouldn't be a huge strain for them since it is not about height but about manners and way of going, but still it makes the horses job that much harder. A lot of riders say that with a riding a hunter it's harder to keep proper equitation because the horse has such a big and rounded jump. I don't believe this is true. I think that too many riders in the hunt and even in the eq ring are trying too hard. I know I am also guilty of this. I find myself jumping for myself instead of just sitting "chilly" and letting the horses motion fold my hips and following with my hand. Many times I will force myself to ride fences as of late and just keep a steady rhythm and pace and let the jump come to me instead of calculating take offs etc. When you let go of many of the technical things it suprised me of how it just happends naturally.
Stay tuned, I am re-reading a good book that I wanted to do a post on , it's called Renegade Champion, the unlikely rise of Fizrada, written by Richard R. Rust. It's a wonderful book written about his mother Jane Pohl who rode on the show circuit with her runt of a TB gelding in the hunters and jumpers classes of the 40's and 50's and breaking gender barriers along the way. Stay tuned.