Flaps
I have been using only one servo, it does buzz when under power but it is normal from a digital servo. I use a high torque Hitec servo with titanium gears, no problem so far, that is with about 130 flights, and I am a big fan of using flaps.
I did plug the original flap hinge holes since they didn't align properly, and drilled new ones to get proper alignment and travel. Otherwise it is a wonderful model to fly and will land in a very short distance when using full flaps. For the same reasons I mentioned in a previous reply, about manufacturing quality, my Corsair center section skin has deformed during the first few flights in 2015 after been exposed to the Colorado sun. It did not affect the behavior while flying but just reflect on the poor manufacturing quality.
I am a builder by heart so ARF are just a way to get some flying while working on serious projects, I hope Horizon keep developing more warbirds like the Corsair, would love to see a FW190 D9!