That is a pretty big case......click here
It seems that all the intake and exhaust venting is done at the front,rear and top of the case.
In the absence of official recommendations......
I would say you could get away with a fairly close fit at the sides of the case providing the sides of the case door were free of the housing you have (as the door has side vents).
Open access at the back of the case and a good 5cm above the case to allow the exhaust fans to function properly would be my guide.If height is a problem though I would imagine the case cooling would function perfectly well without the top blowhole fan running at all....in which case you could probably get away with a close fit at the top as well (but ideally don't do this).