If you’re wanting to give Zen another chance, Zen has a “Focus” mode (Ctrl + Alt + C) where the side bar goes away, giving you essentially a full-screen (and centered) experience. You can still access the tabs by mousing over the left side or the shortcut Ctrl + Alt + S and it’ll fly in, but that might annoy you more than the window being off-center… I think it’s slick though.
Thought I’d mention this in case someone else might want to try.