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Essentially its how Bike Friday makes their bikes now.. threadless fork incorporates its own preload of a threadless headset

with 2 clamping bands around the fork steerer.. Upper one blocks solidly, lower one is a cone-ring, collar .. combination gets wider, as you tighten the bolt.
outer conic forces inner cone downward, being blocked from above, that inner ring presses down on the upper headset..

and above that the handle bar mast, is removable, for packing to travel ...
using a scheme like that, you can use a 1" quill stem inside such a combination, if you wish..

I Got one of the Lower conic band camps and upgraded the original Tikit threadless headset adjustment Scheme, on my bike,
they used a 'problem solvers' adjustable spacer which gets wider by threaded parts...


maybe that and one of their locking spacers
can work for your application...