As recently mentioned ASRock was smart enough to not implement IGP passthrough on the E3C226D2I. Bummer 😦
So I had to find a super slim graphic card which shall fit to my setup. The NVidia NVS 295 was the one I choose in the end. But also then I had to do quite some tweaking. If you look at the picture below you will see that there is not a whole lot of space between the motherboard (bottom of the picture) and the PSU (top of the picture), and exactly between this space the NVidia NVS 295 was planned to sit.
The first thing I actually had to do is to cut a hole into the backplane of my chassis, as the chassis itself was not supposed to support any PCI extension card 😐 .
Then I had to cut the metal bracket of the PCI card itself for fitting:
And the whole setup together: