I was just looking at that earlier today, but didn't have the guts to try and snap it. Thanks for posting this, I may give it a go here in a little bit, if I do I'll let you know how it turned out.
Well, that didn't take me too long to decide to give it a try. I heated up the rubber armor by dipping it in hot water, to give it much more flexibility while working on breaking the tabs.
I broke the back tab first by pushing it in from the outside, then I slowly worked the glue loose around the rim of the dome. Finally I had to pull and cut away the front tab using a razor.
I also went ahead and removed the back tab by once again heating up the rubber armor and slowly working a razor in between the tab and rubber.
So far it seems to have worked great. The dome is held in place tight enough that I don't have to worry about it falling out, and it still seems completely water-tight.
I went ahead and fill the dome completely with water (no bubbles) and will leave it that way for at least 24 hours. If no bubbles have gotten in by tomorrow night I'll say this was a complete success! Thanks again for the tip, I love having the option of turning that head.
Of course, it really makes you wonder why mattel didn't do this in the first place. Put a lip around the bottom rim of the dome, put a soffit facing inward on the rim of the armor and boom, you have a head that can turn and stay in place.