Well that's very interesting and prompts more thoughts. If Arwyn is correct and they start life as true, I've never needed to handle/inspect a new item, And they are in-line and accurate circumferentially, is it possible that the insertion of the bushes has distorted the tube alignment. Assuming that the tubes are supplied in tube form rather than being turned from solid bar stock they will have a weld line which will be harder than the rest if the tube. Thus any stretch distortion will not be equal throughout the total circumference of the tube and this could shift the bushes out of line with each other. and necessitate the need for them to be line reamed for final sizing and to bring them back into alignment for best function. There are a couple more options that may cause this misalignment through installation of the bushes and are we sure that MMC had issues form the welding process/assy of the hub or did it occur when the bushes were installed!
Unfortunately your assessment falls down Sewin - the kingpin tubes are CDS (cold drawn seamless) so no weld line and therefore no distortion!
Would need to be a good grade of glue to hold the bushings in with the loads on the stub axle.
Can't see what the problem is with pressing them in and reaming them to size! It's been that way since 1910.
Interestingly, I've a Manx Norton swinging arm on the work bench at the moment, rider wants phosphor bronze swinging arm bushes making and pressing in because he feels the previous iso-elastic bushes aren't precise enough at speed....
Arwyn
