Mode 3 on most radios except Futaba, as I recall, is a left handed mode 2. I fly this way. The aileron and elevator are on the left for use by a southpaw's dominant hand, just the opposite of a mode 2 radio. Mode 4 is a left handed mode 1 with aileron and throttle on the left.

It is not a valid comparison to compare full scale to RC since a different muscle group is used. In full scale, and I am a retired USAF pilot and instructor, you use the shoulder, arm and wrist, the large muscles. RC flying uses the fingers, small muscles, and is more akin to writing than full scale flying.

Many years ago I published a book of RC and during my research, I got to know a human factors PhD. We discussed this exact thing. His opinion was that most people were fairly ambidextrous with the large muscles, but most were not with small muscles, especially under stress. This is probably the reason I never had any trouble flying with a stick in a fighter or trainer.

All that being said, did you know that Chip Hyde is left-handed and flies right? When he told me that, I remember thinking that he would be really good if he flew southpaw!