I got a BBB stem raiser, being an internal quill , it also functions as an adapter, once wedge is tightened,
spacers are slipped over, and the shim from 1>1.125" , then the threadless stem grips the shim,
it worked... , my situation threadless , too short.. the clever bit is the steel wedge bolt, custom forged..
the 6mm allen hex socket is itself internally threaded, for the top cap bolt , that adjusts the headset preload.