with using washers though, it depends on the size of you're engine

for a size .12 engine say, the mount is small so putting in a washer will give it a few degrees of right thrust because its a small space if you get me.

With a size .90 engine, the mount is much bigger so 1 washer will not give as much right thrust as it would with 1 washer on a smaller engine.

Its like if you had a long plank of wood and a book. Rest the plank on the book and move the book furthur inwards, you'll notice the plank will slant more and more as you get to the end of the opposite side of the plank