MagnaGlide bobbins are great! They take up a lot of the backlash. I would use them before the washers. The other thing that makes me ask is: are your bobbins pre-wound or are you winding your own? The ones you wind can be less consistent and could be causing you some grief. If you're using pre-wound, make sure you clean under your bobbin tension spring more often. Whatever the "glue" is that they use to make the thread stay in a doughnut gets under the spring and causes funky tension too.