Before I answer your questions I just want to let you know this is my first armor build.
I have not trimmed the pivot point, but I do think it’s supposed to look like one piece.
Several people in the forum mentioned using plumbing caulk to fill in the gap, and it’s called an acrylic caulk with silicon. It sets up with some give to it, and it can be sanded and painted. If you get straight silicon caulk you won’t be able to paint it very well. Also it might not show up very well in the pictures; while the caulk is white, it is has a very slight yellow color to it. So I’m using a Rust-Oleum auto light grey primer, and Rust-Oleum gloss white paint to repaint the helmet. Which was also mentioned by a different member in the helmet forums.
Another part I found out through the forums is to basically use E6000 glue on pretty much everything.