One of the difficulties with the fans on top of the radiator is that the rear port ended up right on center with the motherboard tray. There is a cutout to work with here, but will most likely require angled fittings, depending on how you might have a loop setup. AIO’s will likely need to mount with the radiator on top.
Another thing to consider if you plan to do a custom water loop, is reservoir/pump mounting. I’m using a DDC with a tank reservoir, but where the hard drive cage mounts, is about the only viable place to put a reservoir and/or pump.
Installing a full custom waterloop with acrylic hardlines in the PC-O5s was actually kind of fun. It certainly wasn’t the easiest install, but I’m quite pleased with it.
The wide open side with the tempered glass really shows off your components nicely.
There’s enough places to hide LED strips that you can keep them out of sight nicely.