I used a Dremel with a small drum sander attachment to enlarge the hole for the wing servo. It's kind of a pain, but by the time you get finished where the servo will go into that hole easy enough, you wind up with what I'd call an upside down question mark shape (?). And it takes considerable grinding away before you get it large enough. You shouldn't have to sand the wing joiner channel. But don't worry about opening up enough for the servo to fit in. I'm surprised Hobbico hasn't addressed this, but the model has been around for so long, they probably feel it doesn't need any changes. If you don't have a Dremel, just buy the little drum sander at the local Hardware store and put it in a drill. A little clumsy, but it should work.

The pushrod support I replaced with two popsicle sticks so that instead of holding the pushrods rigid, they can slide within a slot, which helps so that there is less binding. Because if you use that support, the pushrod will have to flex at those hole locations. With a slot, the pushrods can move without being hindered.