A spiked hawk will work at that length. Just check out my pic. That was from a long time ago so my mohawk is begger now, but it works at that length. I usually use hair glue instead of spray when I do spikes.
I won't do spikes on mine unless its 7 inches or more. I think short spikes look kinda silly. And when you're hair is below 7 inches its so easy to fan that I'd rather just fan it.