Just as a FYI, I was just looking at a WTB single speed wheel with thoughts of running a few gears on it. When I tried slipping a few cogs on it, I found that where the wide spline forces the next channel to be narrow, it's on the opposite side of a normal hub.
You have to put the cogs on backwards to fit.
I assume this would make it shift like crap since it would be like having no shift ramps.