It's very much a personal preference thing - this is what works for me

I just use the dual rates but I don't follow what appears to be the generally accepted convention when setting them up. I have the high rates set with the switches towards me and low rates set with the switches away from me. That way, If I get into trouble and need to quickly flick back to low rates it is a simple finger movement without interrupting the pressure on the sticks. (It's what works for me and I've always done it that way).

I find that for first learning to 3d (and we never stop learning) it can help to just have one surface set to high rates (Eg just the elevator when learning a simple Harrier) and you still have gentle movements on the other surfaces.

I use around -60% (on a Hitec Tx) Expo for my 3d rates but I believe that it is common for people to go to around 80 - 85%.