(THE SCREENSHOTS ARE NOT 100% ACCURATE. My dragon print is scaled to 125%. The middle bit of the spring is different to allow clearance for the string.)
Didn't like the eyes that needed to be glued in. This one not only makes them both one piece but adds a spring structure so you can snap them in. It also sets the proper 45deg angle so the eyes are looking forward.
Insert the eyes before the jaw and after you've run string through the neck. Be sure to be careful of the ball joints for the jaw (broke one of mine off, still kinda works though.) You can nudge and adjust them into position with a pointed object like tweezers, needle-nose pliers, or the eraser end of a pencil. Be careful you don't stab yourself.
Any, but 100% worked for me.
Print the eyes the same way they are oriented in the file (pointing forward, spring horizontal) with supports to ensure the spring doesn't split across the layer line.