P3steel x axis carriages and belt tensioner

I re-tweaked an existing design from the Prusa to fit the P3steel. I realized that some of the current designs for P3steel are not accurate (the lead screw circle and the 8 mm smooth rod circle were not co-linear in some of the designs).
I also reduced the gap in the belt tensioner piece to snugly hold 2 flange bearings (F623ZZ).
You don't need support to print these parts and the dimensions should be fairly snug to avoid any excess play. If some of the holes were a bit tight, just use a Dri