I'm not so sure about the attributes of the so called `Diamond' stabiliser. I fly an Astro Hog, Orion, Taurus, Concord and Superstar, all with what you would call a `diamond' tail section and I have yet to detect any `soft neutral' effect. This in comparison with Nimbus, Perigee, Atlas, Super Kaos and Curare with the `standard' symmetric section. Perhaps you are confusing this with the `negative expo' effect of rotary servo outputs...
Evan.