There are different ways of extending steering collumns. If the extension is so to speak, at the diameter of the stem, as it seems to be in this case, then it replaces the stem, and any spacers or hangers remain where they were with the stem, unless the extender does not have enough clearance for them. The extender, unlike the stem is not a passthrough fitting so you have to take that into account, you can't force the extender below the level of the steering tube and put spacers above it, as you can with the stem, so you have to emloy common sense when installing it.
The actual stem just fits on the extender, as the preload is all in the extender.
If the extension is at the diameter of the steering tube, then it basically assembles as it would if it were just a long steering tube.
Last edited by MassiveD; 09-29-12 at 03:28 PM.