GUI scaling scrollView Content

I can only extend the anchor points on my scroller content to the size of it's parent which is a mask and only 1/4 the width of the content itself.

As such when the scene is rendered on different screen sizes the content of the scroller is wildly different than the other gui objects.

I thought I could add a script that resized the content panel manually but I can't find the width and height of the rect transform on the mask. all I can get are the anchor points which don't seem to ever change.

Is anyone else using a scrollView in the screenSpace? how are you sizing it's content?