i find dual rates dangerous and really not worthwhile. (I don't use them on my 3d planes even, some have close around 65 degrees of elevator travel!)

the problem is that now the flight envelope of the plane changes with different rates. Instead, use expo, lots of it if needed, and better yet if you have a radio that allows dual expo settings instead. you still have the full throw of the servo if you need it, but plenty easy to fly around in normal flight