I like PeterNZen's answer and mostly agree. I feel like to much expo, especialy on Aileron will not let you hit a constant roll rate everytime. The more expo, the farther out in the stick you will have a "knee" where it will be too critical to hit that exact spot, a little short, the roll slows way down, a little past, the roll speeds way up. I set my ailerons to the fastest roll rate i would need or want, and then about 5 to maybe 10 percent expo. On elevator I use about 20%, for rudder around 25 to 30 to make those nice corrections that the judges cant see (hahaha)