Ultimate i3 X belt tensioner

I came up with this part after pushing the limits as fast as I could get my printer to go, and having issues with lots of vibration on the top span of belt no matter which tensioner on thingiverse I tried so I broke down and made my own. This requires a idler wheel.. I used one with 12.2mm diameter, 18mm flange and 5mm ID.

Assemble by putting the idler wheel on the bolt, a nut behind the idler, then put the bolt through the slot and add a washer and nut on the back side. A butterfly nut makes