I think the gentleman who wrote the web piece in question is mistaken about having to go to five cogs. The instruction manual that comes with the device shows installation with a six speed, which can even be seen on the website.

I could never get the thing to work perfectly with 5 speed or 6. The chain rubbed on the hanger while in the small cog/6 speed, but with the 5 speed the gap was too large to easily jump from the small cog to the hanger. I assume that the makers of my frame did not get the spacing perfect, or perhaps my hub spacing was whacky.