Actually for gymnastics for horses you tend to work off a 9' - 10' stride as the idea is to make it easy and the jumps low. For a pony that would translate to 6' (very small pony) - 9' (large pony with horse-like stride).
Bounces are usually set tighter so that the horse isn't scrambling or learning to jump flat.
One strides will vary based on what you are working on. At shows obviously they can get very tricky. I like to work on tight ones to get the horse snappy with their legs.
Great article on a gymnastic prepping for combinations on course: Getting Started Over Triple Combinations
From sally swift's book distances of gymnastics: Centered Riding 2 - Google Books