RE: Ailerons on just the top wing? Can of worms?
The PT-17 Stearman is one of the most popular of all scale bipes, and only has ailerons on one wing (lower, in this case) Many of the best WWI models (and full-scale) only have ailerons on one wing. (Dr-1, D-VII, SPAD VII and XIII, Nieuport 11, 17, 24, and 28.
All are great performers as models. I can't tell a lot of difference in my friend's 1/5 Stearman's roll rate compared to my 1/5 Waco's roll rate. Easier to keep the appearance clean if the ailerons are on the bottom wing (No wires showing), but there are ways around that.