[UMG] Using Slider as Scrollbar - Thumb Size problem

Hi there.

I tried to use Sliders as Scrollbars, to get more freedom in using visibility, Stepsize and Positioning.

Now i´ve a Problem with the Size of the Thumb.

Like as a normal Windows Scrollbar, i want the Thumb to be more to a 1.0 Size of the Full Bar, when the content fits into the View. Means: The Thumb is getting Longer, the less Space is needed in the Viewport.

So i created 2 Canvas Panels. 1 a s Viewport with Clipping.
The second a Viewport, that sizes to its content, and as child of the first Viewport.
I called them:

>> Panel_Viewport_Content.

I now placed a default Slider as horizontal bar below the Panel_Viewport, And another one as Vertical Scrollbar at the right side of the Panel_Viewport.

Now i tried to calculate the Thumb Image Size of my Sliders (Scrollbar_H, Scrollbar_V). This is the Blueprint:

The formula would be:

Thumb Length = ScrollbarSize * ((1 / ContentSize) * ViewportSize)

The Code for Scrollbar_H is nearly the same, except i use the X values. Just Thumb Image Size is always using X for Length and Y for thickness.

So… the result is, that this is working well for the H value…
But, the V Scrollbar is stretching the Thumb as expected… but always showing it on the upper right - clipped outside the Window/Screen. You only see the bottom 40-60 Pixels of the bar. I can drag and drop it down, and it has the full length… But it seems the aligment is messed up…

Any idead, what could be wrong?