I have an Arctic Freezer II 420 A-RGB; the radiator is 38mm + fans are 27mm (total of 65mm). I have found that if mounted at the front, the pipes cannot reach the CPU (fault of the AIO, not the case - although the PSU shroud needs to be removed for the pipes to exit the base, which makes the inside look a bit ugly), but when mounted at the top, as @HBSound illustrated, the unit protrudes into the I/O panel space making it impossible to fit the motherboard.
Specific to my issue and AIO, I have found that these cases have a bigger "head height" that allow for top mounting the AFII 420.
Some people have been able to use the Lian Li Lancool II, but only if their overall motherboard height is lower than 40mm. My motherboard I/O and MOSFET heatsink is 50mm, so something readers need to consider.
@HBSound - What case did you end up going with?
Thank you for the update.
I had been searching for a small case to fit a 12 x 13.2 motherboard, but my search proved to be exhausting. While I thought BQ would have an appropriate case, I was unable to find one. However, I must say that BQ's customer service was exceptional. They were very helpful in answering my questions prior to and after my purchase of the 800 case.
It was only after I had the case and started to test fit the motherboard that I discovered some space issues with the front of the case that were not mentioned in the specs. I shared my findings with BQ, and they had no idea about the issue. Then started posting via social media about the front of the case restrictions. I was experiencing some issues with my PC building and read the same issue with other folks, so I did not feel to bad. I hate I wasted my time. It seems that companies like BQ and Lian Li do not consider the feedback of regular users while designing these cases.
However, if I do decide to look for another case, I will consider the Silverstone RM51 and RM52.