I searched for a 70mm fan holder/case for the original psu of the AnetA8, but I didnt found any. So I created one in Fusion 360. And yeah it fits :D
But until now I cant give you any evidence that a 70mm fan will lower the temperature of your psu, because I have not tried it yet.
Definitely you should use support while printing and maybe a little brim or raft if you have any warping problems :)