Interesting question, I have been thinking about this recently as I have bought a Pinnicle off an experienced Pattern pilot and copied his settings to my radio.
I never flew with any expo on my last pattern model and did suffer some days with wagging wings an I used the throttle. With the Pinnicle, his set up had 100% expo, I found this VERY hard to fly with. So I took off the expo and reduced the throws, I'm back to wing wagging though. Another experienced pattern pilot suggested that 25% would give a more linier feel, while still making it "soft around the centre". I will give this a try next time I practice. Matt