Rendering with transparency with composure plugin


I am trying to add a CG character to a filmed footage that I have imported into UE. I just want to render the character with his shadow (transparent background) so I can composite this in After Effects. I’m using the composure plugin to overlay the CG character on the footage. When I preview the comp (from the composure) it looks perfect (first pic), but I can’t find a way to export it without the background footage.

I have also tried to export it altogether (Character + footage) using the output pass, but the exposure and contrast gets messed up:

Is there anyway I can export just the character with the shadow on a transparent background?