Here are some pics of my 45mm thick Alphacool 420mm with 25 mm thick fans on it. PERFECT length for this case if you ask me. I'm not a big fan of the radiators going past the top of the motherboard look. Plus it requires you to take off the top radiator to remove RAM, remove fan inputs from the CPU headers, remove the 8-pin CPU power connector, etc.
I actually did try sticking my Alphacool 420mm Monsta on the top when I had my motherboard in and it did seem to fit after a lot of PITA twisting and turning. Looked terrible though!