Control an image fill, using another slider, via the inspector

Using Unity version 5.3.1f1 personal, vanilla project (no editor addons etc)

I have a canvas, I have sliders, I want a level bar visual to adjust with a slider, so when I slide the slider at runtime, the image fill slides in unison.

I want to do this using the inspector for the Slider.

I use the 'On Value Changes (Single)' section press '+', Drag in my power/level bar object Change the function to 'Image.fillAmount'

When I use the slider, it does change the fill to whatever value I added, but its not variable or reversable, just changed and doesnt change back while at runtime.

What am I missing? No script ideally, Im sure this can be done this way. Surely...

If all else fails, does anyone have a quick script that can tie several image fills to one slider?

Slider

Image with fill (level/power bar)