Soooooo, the neck mechanism in it's current version does not work. I have one or more joints that need to be changed to a revolute joint instead of a spherical joint. I've been working all day yesterday and today in order to find a working design.
For the past few hours I've designed a new mechanism using derailleur cables, cylinders, and pistons... it worked in theory but it would be too time consuming and costly to actually fabricate it.
Just after giving up on that, I found that a simple tweak in the current mechanism will work apparently. I have to look at it more in Solidworks to make sure it really works out...
I will give an update later tonight if I get a chance to finalize a new design for it.
Edit: It seems that it will work in theory. I just need to find the correct length of the rods and their locations relative to each other. This will take a lot longer than I thought... I'll leave it for tomorrow.