I simply made a template, starting with the paper one in the Tortoise package. Add a right angled piece of brass wire to represent the Tortoise actuator taped to the template. Then:
1. Use a 9V battery to run the Tortoise to mid-position.
2. Draw a pencil line under the turnout directly in line with the centerline of the straight through path of the track above.
3. Temporarily fix the throwbar at mid-throw with wedges or tape.
4. Position the template under the turnout with the actuating wire poking up through the throwbar. Adjust the position of the template so that the actuating wire is perfectly vertical in both directions.and is centered in line with the track marking.
5. Then use an awl or pen/pencil to mark the screw locations in the 4 corners of the template. Use a small nail to punch screw starter holes.
6. Replace the template with the Tortoise machine with the actuating wire poking up through the throwbar. Add 2 mounting screws in diagonal corners.
7. Remove throwbar wedges and verify operation using a 9V battery.
8. Fine tune position if necessary. Add the other 2 screws. Re-verify operation. Trim Tortoise actuating wire flush with top of throwbar.