This all worked but when I start GSX services the positioning of the cones are clustered around the main landing gear rather than protecting the 4 corners of the plane.
Traffic cones are always relative to the airplane position, but they are not dynamically linked to the plane, they are only created in the correct position when you initially park the plane.
Which means, if you made a quick edit to the scenery, you might still see the cones which were created in the original position, so it's usually best to always choose "Restart Couatl" after editing the parking spot, then if you select the gate again, the cones will be regenerated in the new position.