Very simple question on alpha channel

Guys... am i too dumb or what ?

I have 2 open exr clips. One as background and one as foreground with an alpha.

I import them. Background clip on Video 1 and Foreground clip on Video 2 above.

But now comes the bummer:

I want to add a simple blur on the Foreground, BUT when i do the foreground object CLIPS the effect at the alpha margins. Well i thought, i just need to check on "Use OFX alpha" but it does nothing.

Look attachment.

What do i do wrong. Oh, i managed to do this in fusion with nodes, but i dont want to, because fusion is slow, and i want to use the color interface.

So the red glow should go beyond the edges not be cut off at the alpha edges.

Many thanks

What is it you want it to blur outside of the alpha margin? Is it the background so it is effecting both? If so then i think you need to make it a compound clip and add your blur to it rather than the individual clips. If you need to control where it blurs you can use a power window.

No. What i want is that the added glow/ofx,etc... expands also the alpha channel based on the added effect, halo. etc. Cause the OFX does not touch the alpha at all, and it has to to be correct.
Even if i right click "use OFX alpha" it wont do anything to the alpha. The same goes for edit mode.