Well I never felt the need to do that, but I don't see any reason why you couldn't if necessary. But I think it would be a last resort. As you can see, I have a rad+fans at the bottom, and it was a little tight given proximity to the motherboard the cables that connect down there, but I managed it fine. There are some holes down there, I think you just need to plan it out, and perhaps even bring some cables through before you install the motherboard. The only thing that would pose a problem is if your USB 3.0 connector was on the bottom edge of the motherboard... it simply wouldn't go in with fans there, unless you had one of those flexible extension cables.
Cheers dude. The more I look at pics online the less a problem I think it'll be. I am planning a bank of fans on the bottom but I'll cross that bridge when I come to it I guess.