As I said, that used to be part of the instructions in all model kits. I suppose it sort of slipped through the cracks over the years. Please do this same thing to your landing gear where the wheel collars go as well. It does not require a big flat area, just enough to allow the set screw to have a true flat area to seat. Otherwise, it's kind of like trying to balance a pencil on a round ball.

Bill, AMA 4720