I stacked 2 washers on the upper left and lower left side of the mount. I don't know the exact size of the washer, but I'd say the diamter was probably 3/8 inch or maybe 7/16 inch. But you may need to adjust that based on the size of the washers you use. But like I said, if I had to do it over I'd use http://www2.towerhobbies.com/cgi-bin...?&I=LXE953&P=7 from Tower. They are only $2.39