I don't know about non-centering nose gear anymore as I switched to
it as soon as possible. Since they are of Aussie origination, maybe
a drop ship to you would be a lot easier than somewhere in the Americas.
Any shimmy is of concern since, if it occurs at touchdown of 170 Kts,
flutter destruction of everything that the nose gear is attached to is
inevitable (and quick). The nose wheel thru bolt should be tightened so
that you cannot "spin" the nose tire by hand (off the ground of course)
any more than 1/4 turn just in case the "judder" is caused by "loose"
bearings..
Now remember that - the bail around the back of the wheel is to
"guide" the wheel into the well should it not be straight. Regardless of the
angle of the wheel slamming into the well, the "finger" on the retraction
mechanism should always trip the sequence valve when the wheel is stowed and
out of the way. Then the door should close. Period. Mr Shattuck's
explanatiion of the delamination possibility should be investigated.