I have a question on the Lake Country 5" backing plate. With the plate it comes with 2 washers on it? Are both of these washers necessary for use, or is it up to the user to decide if they want one or two? Reason I am asking is bacause the standard 6" plate that comes with the 7424 seems to have a longer thread on it to attach to the machine compared to the LC 5". I figured I'd ask since I am going to be using it for the first time, and I want to make sure that I am using it right