It's made of two each of two parts, the roller is printed vertically so it is properly round:
(These are shown pre-slicing, without the raft and support.)
For the pivots, I have decided to standardise on 3mm dia. x 10mm dowel pins as a stock item. Polished steel against plastic makes a pretty good bearing. The dowel pins press-fit into the rollers, leaving 3mm exposed. There is a 7mm limit stop formed in the roller, but usefully an M4 nut is 3mm thick so slipping the nut over the dowel pin provides a positive limit stop when the dowel pin is pressed in with (eg) a vice. The centre hole is also a little larger at the surface to locate the dowel pin before pressing it home.
For anyone who doesn't want to purchase proper machined dowel pins (available on eBay), I have found metal skewers a useful source of plated metal rod (available from supermarkets and discount stores), but I have also drawn up some tapered pins which can be printed and inserted instead:
There are a couple of problems, caused by warping. The minor of these is that the flanges on the roller did not print as a uniform thickness, somehow the underside of the flange pulls away from the support:
However, the base itself has not come out flat. The print did not lose adhesion from the bed, it lifted the magnetic plate!
The result is that the weight of the reel on the roller rocks the base on the warping, and the telescopic joint between the base sections wants to lift. This doesn't stop it working, but perhaps if I reprint that part on its side that will cure it. Worth a try, anyway. I don't have any ideas about the flange warping.
Anyway, it does the job, and better than my Mk1 (which wouldn't take my narrowest reels, wasn't adjustable for diameter, and was too thin a structure so broke). I'll try printing the base on its side, and then find a way to make the print files available.