The launch lug location had already been marked and masked on the tube. The engine hook will line up with the launch lug.
The engine mount in now glued in place.
Some instructions will have you place a bead of glue inside the tube, 1" from the end.
Because these centering rings are thin, I tried to place my glue ring closer to the place where the upper ring would eventually sit. This was farther inside than 1".
I used a rounded dowel to roll a bead of glue in the tube.
In the above picture, my sanding block was used to evenly push the mount into place. The flat side of the block insured the end of the mount tube was even with the main body tube.
The engine hook extends beyond the tube end, the block was set a little to the side of it when pushing the mount in place.