for a trainer suggested manufacturers rates. dont worry about low/high expo etc etc etc

first off if the student over controls the plane its something he needs to break himself of before he can really learn to fly so low rates only delays this proccess.

expo really no need for it on most trainers cause they arent that touchy.

when do you need high/low rates and expo

i dial in about -20 to -40 on most of my planes for personal feel. its not needed but i like it with the exception of 2 planes. my pizza box and my somethin extra there im using about -50 to -70 expo for the simple reason that i have the throws set to maximum (not max recomended, max phisically possible with the surfaces) and those planes if i put the sticks in the corners im doing something stupid so it doesnt matter if the controls "jump"

as for dual rates i dont use them (dont have any planes that really need them)

but fot fast planes were you need high throws for take off and landing but need small thows during flight or 3d planes that need smaller throws for "normal flying" so as not to snap or such.

but that is just my opinion its really up to the person flying... if you want a rate for takeoffs and landing and a rate for flying then use it.. if you arent comforatble with your setup then "tweak" it till you are. you have more fun that way

but again... thats just my opinion