Looking around at mods people seem to be cutting big holes, to fit multi-fan radiators. I am presuming that one 12" fan/radiator is not enough to cool a modern graphics card and processor which is why they are doing it. An example of current thinking. Which I think looks ugly.
However cases often have more than one fan mount point. Any particular reason why people don't use multiple radiators? In an arrangement something like this. This would also cool after every hot component rather than get rid of lots of heat at the same time.
Pump (at bottom)
Graphics card
Radiator back of case
CPU
Radiator blow hole
reservoir
(Could do a Radiator front of case too), but would prefer a clean air intake.