Presumably jimihendrix accidentally put 'steerer tube', when he meant 'head tube'.
No, the ones i was thinking of fit on the steerer tube, i have a pair to use the 1 1/8 steerer forks with the 1 1/4 headset and headtube on my Manitou, crown race one is a steel collar and the top is a split alloy sleeve, never used them before though, hope they work
I'll stick a pic up later if i get the time
Sorry to intimate that you didn't know your terminology then. I would be interested to see this. Obviously introducing more dynamic surfaces requiring tight tolerances is not ideal (part of the reason integrated h/sets are wank), but the crown race arrangement sounds particularly worrying. Depends entirely on how the bike will be used, I suppose.
Do let us know how it goes.