Very good job!
I wanted find something simple and powerful to replace my old (but beloved) Thumbnail Zoom Plus,
AND it seems i find it!
It does the job without need to battle with its configurations.
The popup of the preview appear at the right place simply and its loading is very discreet.
I appreciate the organization of its options (and their clear descriptions).
It have some others powerful use, easily accessible.

Just a request:

It's possible to toggle on/off just by clicking its icon (and not click to open its menu and click "disable" / "enable" to toggle it ?
And add a caret to its icon to open its menu of options.

I don't need to change its options all the time, but often toggle it for different sites...