Updated with all the required STL files to implement the belted Z axis layout as shown. Other files used in the build, but not critical to the Z axis are listed as remix sources.
This thing is a small remix of the original tensioner files by Kldz to make it slightly easier to print. The parts have been reoriented to lay flat on the bed and a sacrificial bridge layer has been added to the tensioner nut holes so that the circular nut holes above them print nicely. Just trim out the bridge layer with a drill or xacto knife.
I used a 1524mm continuous loop belt and moved the position of the lead screws and motor mounts forward and adding a lead screw at center rear. I was also able to use 400mm screws without issue. In fact using the longer screws meant they got in the way of the print head at the edges. 400mm keeps them below the plane of the print surface. See the photos for how the bed mounts were positioned to get everything lined up with clearance.
I've also linked the other remixes I've used in my build for those interested. The most important of which was modified two-bearing Z mount for three-leadscrew Z axis system for D-bot by Rexipus.
More details about the printer build can be found here: https://forum.duet3d.com/topic/5282/my-custom-d-bot
Don't forget to check out my Titan Aero carriage for the DBot. https://www.thingiverse.com/thing:2849355
0.3 layer height, 0.6 nozzle, 5 shells.
The part is put under quite a bit of tension and torsion from the belts, so print it strong. Also make sure to use M3 washers on top of an M4 washers to spread out the pressure when mounting the motor.
I used PLA and after several months it has started to flex a bit and spread out around the motor bolts. Still functions normally, but you may want to print in PETG or ABS/ASA if you can. And print it nearly solid. At least 5 shells.
Remove the sacrificial bridge layer.
Just trim out the bridge layer with a drill or xacto knife.