Time to put the servo-plate together with 2X 8mm M3 screws.
Tap the holes if you prefer... or not. Just take it slow so that you don't crack the plastic.
ABS is a little more forgiving than PLA when you use the force.
The screws should be flush on the servo side so the servos sit nice and flat.
We'll use a short wood screw to hold the dowel in place.
You'll have to make holes in the plate for the screws that hold the servo in place.
A silver Sharpie works great on black PLA.
In some cases I prefer to 'drill' using a long hot soldering iron tip; it adds a little strength around the hole.
You might have to remove some of the mushroomed plastic around the hole so that the servo fits flat against the posts.
Test fit the holes with a screw to make sure that you got the width just-right - not to tight and not too loose.
The two pieces that form the neck should rotate freely.