ORIGINAL: Farmer Ted
1st: Is it normal for bipes with dual ailerons to have different throw from upper to lower ?
(just due to the arcs that the control arms travel through)
Yes and no. You will NOT see any biplanes have such screwed up throws except the ones with paired ailerons, where one aileron drives the other. It simply does not happen with any biplane that drives each aileron with it's own servo. And it is not something that would be copied on purpose. There are no positive benefits of it. So the bigger bipes that use 4 servos are not going to have the problem and you can bet your house and car their designers won't be showing how you can adjust your radio to get f'd-up deflections.
2nd: if this isn't normal, what can I do to fix it?
See the above posts and the other thread.
3rd: if it is normal, which ailerons to I set the throws off of, upper or lower?
It's not which ailerons drive and which are driven, it's the design of the rigging.
4th: do any bipe flyers recommend expo on the aileron servos?
The expo or not decision isn't really related to biplanes versus monoplanes. Expo is really useful for most people on elevators. It's slightly less useful on ailerons. And that depends on the airplane, not the number of wings the airplane has.
When landing, you know how delicate you have to use the elevator. Well, that's what expo helps with. Think about the maneuvers where aileron control needs to be delicate like that. People flying very precisely do correct with fine precision with the ailerons. That's what expo would help with on the ailerons. Do you want some help there? Go for it. But it's not going to make the airplane less prone to yaw variably like this aileron problem causes. And it's not going to make the bipe with these almost random deflections less apt to suddenly lose a wing in the turns or during hard pitching.
This deflection problem probably most often manifests itself as an airplane that unexpectedly does things. Is apt to snap out of a maneuver without warning. Has to be watched closely on landing if you're a bit slow because it just might drop a wing if you're curling it in instead of bringing it straight and level. Things like that.