I am also building a GP RV 40 Sport Scale, and according to the instructions manual
for the engine mount ( Mark the location for the holes for mounting the engine mount.
(Hint: The great Planes Dead Center" Tool (GPMR8130) works fast for marking these holes! On the marks you made on the engine mount, drill a 7/64" hole into the engine mount. After drilling the hole. tap each hole with a 6-32 tap. Once tapped, mount the engine to the mount with four 6-32 x 3/4" socket head screws and #6 washers.) well I'm not there yet but just reading ahead. Hope that helps. Good luck

roltech