I have both a computer radio, and an old 6 channel Futaba non computer radio. Both have dual rates. I use dual rates a lot, but have been advised by many veteran pilots to not use the expo or any form of mixing etc. until I have mastered conventional. Their thinking is that although it will make things easier when flying close to center position, it will also be a crutch to a learner, and make him dependent on it. I am heeding their advise. Now one thing that I did do that seemed to help me a lot was extend the length of the sticks approximately 1/2 to 3/4 of an inch. This in effect makes you move your thumbs more distance to get a given reaction. But it is not expo as it is the same throughout the range. It just seems to help "slow things down" a bit, and I progressed much quicker once I did this. I guess this is still a crutch in a way, but it works for me.
As they say on commercials, (your results may vairy

Dwight Hayden