WPF Scale Transform and ScrollViewer - Cannot scroll beyond original size when scaled

I have a StackPanel inside a ScrollViewer.

I have a slider that does a scale transformation on the stack bar to be able to scale and scale. The problem is that when I zoom in, the scrollviewer does not consider the content to be "larger".

So if I scroll down a bit and scroll as far as I can go - it stops me before I get to the end. If I go back to the untransformed level, I can see that it stops exactly at this stage. If I zoom in a lot, I can only see a small portion of my overall content when I scroll all the way.

I can change the TransformOrigin to control which side is losing the most content; but I suppose there must be some way for the scrollviewer (or other control?) to take care of this for me.