It's taken me a while, but I decided to pick up a Galvatron, and, like most folks, found myself disappointed in a few aspects of the toy. The one that drew the most frustration from me was the neck. While I researched various mods to improve the neck articulation, many involved neutering the Titan Master functionality or required much more work than I would like to invest in. I'm not sure if anyone else has done this before, so I went into this blind.
The main issue Galvatron's helmet/mask has is the plastic between the hinge and the part that covers the face. Due to the clearances, the sides of that connection immediately bumps into the edges of the very small gap Hasbro made for it to move. Although the main issue results from the connection of the mask and spring-loaded hinge, I opted to modify the body, mainly to retain structural integrity of the helmet as the neck rotates at the risk of making the body's own structure slightly weaker.

(Pardon the mess, the main part of this are the extra grooves)
Although you still result in a helmet that sits some distance away from the face, you gain enough articulation to match the other Voyager class figures in Titans Return with their torso additions up.

I hope you consider this mod if you feel your Titans Return Galvatron needs to be a bit better!