If you like to experiment, install some boost tabs on those ailerons. You will then find that even 30 in/oz servos will be more than adequate. Make them 8 to not more than 10% of the aileron surface area. I've flown 1/4 scale Gasoline powered biplanes with boost tabs and 30 in/oz servos with no problems. Even better, add some mass balance to the ailerons as that will take a lot of the stress off the servos, especially on hard landings where the weight of the ailerons put an undue force on the servo gears.