March serp belt pulleys with factory brackets

I saw a dude with a skateboard wheel on the end of a stud acting as a tensioner (although it was static, doesnt move) he put it against the belt on the outside of the belt path as belts like to grow there when they get humming. I didnt ask what it did as I kinda figured it out by looking at it. Doing some math, I figured the 54mm skateboard wheel would rotate at ~28000 RPM at cranks 7000 RPM, with a belt speed of about 233 ft/sec. really was a simple idea, just find a 5/16 bolt that you could extend out and bolt a skateboard wheel to.