Washers? Do you mean the brass grommets? They need to be there but that is not causing the buzz. If you are adding extra washers above the grommets, that is OK but won't help the buzz either. If you are only getting the buzz at full throw I would not worry about that. You will be in that condition less that 0.5% of the time and probably much less than that. Try reducing your EPA 10-15% since you are going to have too much throw anyway for steering. If your radio has exponential, you may want to use that too. Will make taxiing easier as well as T.O. & landing.