ORIGINAL: Geistware
If you want to add right and down thrust then in facing the engine, place a washer behind the upper right mount/standoff for the engine. This will give up more right and down thrust.
"Upper right" is not quite correct. When talking about left and right we should refer to the sides of the plane looking in the direction the plane flies. So in order to add right thrust the washer should be placed behind the upper left mounting hole of the engine mount (between the engine mount and firewall). In fact I would place two washers there, one between the upper right engine mount hole and firewall, one between the lower left and none between the lower right engine mount hole and the firewall.