I was not expecting these to print well, planning to have them done at Shapeways, but took a test-print at home anyway to check clearances. In fact, the home print has worked very well. It seems the Mars Pro is better at spindly things than chunky bits.
The pull-rod in the centre of each assembly seems to have come out thinner than expected relative to the parts with rectangular section. This seems to be a feature of the printer (or the slicing software), that the round parts shrink in on themselves. In a production print, I will thicken that part to compensate.
The strategy, as with the SECR coaches I'm building, is to cut a gap in the cross-member such that the assemblies fit over the axles with the printed pull-rod passing beneath its axle. The rods to the centre crank will be added from wire when the brake assemblies are fixed.