When I assembled my new frame a few months back, I machined a one piece tapered steerer/stem spacer from a piece of delrin/acetal. The stock spacers I had were very clumsy looking.

At the time I did consider the material choice and concluded that being loaded in compression only it would be fine. Carbon spacers are commonly used, the epoxy giving the compressive strength and in this respect delrin must be about comparable with Epoxy. I chose delrin over alloy as it is black and will not tarnish.

I have been riding the bike for months now with no problem, no loosening of the headset etc, but for some reason I am now having doubts. Does anyone have a view on this?

Spacer can be seen in this pic: