Did you use the quill type with a threaded or a threadless steerer tube? If the second, did you have to remove the star nut so that the extender could go deeper into the steerer tube?
On my internal BHP 21, yes I removed the star nut, (you can drill the inner edge,
or the center comes apart, it breaks, if the pull up, is strong enough
[steel steerer] nut retained in star with aluminum 'rivet'..
then i turned 'the stars' on edge and they come right out)
the Clever bit, is not shown, the center bolt, .. custom manufactured for this part,
it has a 6mm thread inside the 6mm hex, so once the quill wedge is tightened,
the top cap bolt pulls against the internal thrad, to do the headset adjustment, as per usual for threadless forks.
the rings at the top are keyed shims the stem grips around, you use all or as many as you wish,
to have a choice of how much taller you are making the steerer..
IDK what needs the OP has , external stem raisers will just shift your single/one stem
to a higher position..
With the parts I got , For Touring, I was able to add a second Threadless stem,
underneath, and there, I mount the clip to QR my Handlebar Bag.
Of course it also may mean you need to replace all the cables
to reach the new higher location of the Handlebars.