That's really my only gripe with the extension, being able to have the popup centred so we can move the mouse around would be cool as well (upon activating the full zoom mode) but just a toggle would be cool, thanks.
Thanks for forking my project. How about sending some pull requests upstream?
Also I'd like you to explicitly mention differentiation between your fork and upstream project in extension description. I've already received issue reports from users of your fork and I don't want to spend my time on those.