There is a fundamental flaw with the case. There is a place for the air to go in, but no place for it to exit. That can perhaps be fixed by just removing the 220mm fan but leaving the fan grating.
The case is very much a work in progress, I only got the PCI-e ribbon delivered yesterday and worked on fitting it in the evening so I am now in a position to look into the ventilation of the case. For example the PSU is currently just circulating air from the inside of the case, and this will not be the case when I am done (I wil be building a cover for above and below the PS to hide the cables and vent the air out of the case).
In my previous cases which also used the same 220mm as the sole case fan had panels with mesh sections, and this was more than enough to ventilate the heat. This might be the step I will take here, but i am as yet undecided.
The location of the GPU is a game changer.
Alot of the top-down CPU cooler I see on the market have the main heatsink offset from the touch plate, the Samurai ZZ is an example of this. So could it not just put the offset to the back of the case instead of down where the GPU encroaches?
If you removed the 220mm fan but left the fan grating, how much overhead space do you have?
I would have roughly 120mm to play with, but the fan is a fundimental design feature of the build and I would be very unlikely to consider this, just by changing the orientation of the GPU from the stadard position, I have cut 10c off the furmark load temp (from 70c to 60c) at 25% fan speeds. And that is even before I have added the required ventilation!
Maybe the Samurai ZZ after all will be the best fit.
I am starting to come to the same conclusion myself.
I will take some measurements and photos of the case with a 120mm fan placed on the CPU heatsink so see how that looks and if the space is easier to determine.