Folks, before you start printing all parts, make sure your printer is calibrated and the slicer is set to let the printer do what you expect. That takes some minutes or more, but it is really, really worth the time. I had calibrated and tested my OrdBot printer and set and tested (there are tons of calibration objects out there in Thingaverse) for precision, scale, tram and orthogonal correctness.
Likewise, the extrusion factors influence your outcome more than you would expect. You will get a much better understanding of your printer during this preparation, and the result will overwhelm you. Be aware that every fine setting varies for different filament materials, even for different colours of the same brand, so make sure you get uniform results.
Allted has provided such an ingenious design here, it would be bad if you screw it up with an ill-set printer. The parts I made for my machine never needed any postprocessing (working with 25mmOD, 2mm wall thickness polished VA (stainless steel) tube normally used in the boating industry). Pluck them from the building platform, put them together, a bolt here, a nut there, and it fits. Awesome.