Really wish the case compatiability was radiator on top rather than bottom, have a feeling that will be V2 of this case
Only three ways to achieve that:
Make the case taller. It'll wind up being around 20.5-21.0 litres.
Allow the case to be inverted, so that the GPU/rad area is up top. But the window will be on the "other" side.
Have a modular rear panel (ala O11 Mini) so the motherboard can be shifted down (GPU vertical) to make space for a rad at the top.