"SPAD" Simple Plastic Aircraft Design

[Celwin]

That sounds strange Kennyglide. I haven't seen your Mikeys Pylon Racer, but I presume that there's a servo for each aileron and that it's a direct link to avoid any flexing. Flexing can occur in a light pushrods when they push. The other area of flex is the horn mount to the aileron. The other thing to look for is that you're using the full travel on the servo, not using your transmitter to reduce the throw when needed.
The wing can't twist can it? The early foamy eklectic Bixlers used to flex the fuselage when up elevator was applied in a high-speed dive,essentially neutralising the up-elevator.