Extreme Flight 125" EXTRA 300 Assembly Manual page 13

21. Mounting the engine is quite easy. There are laser inscribed reference marks on the
front of the engine mounting plate. When looking at the front of the mounting plate the
vertical line to the right of the center line should be used to allow for right thrust offset to
counter spiral slipstream effect. The distance from the face of the engine mounting plate to
the engine drive washer should be 8 1/8 inches. Use standoffs to achieve this length.
Here are a couple of photos showing the installation of the DA-170 in our Extra.