I dont have the Luxury of 2 nearly identical bikes but for that one difference,
in order to have a proper comparison, I used the BHP21 to regain the height lost to the hacksaw
in a distant prior build up, of this bike ..

The Quill is a strong extruded tube with a keyway slot,
and the stack of shims are made with the matching key tab.

Another solution, common in most Wholesale parts inventory a LBS can order
is a steel tube made to have a smaller diameter on the bottom .. ID of fork
and a larger OD at the top.. you could insert another quill stem, or you could
add a few shims and clamp a threadless stem around that .

from Harris site probably from QBP, wholesale
Stem Raisers for Standard Expander/Wedge Stems $19.95



See:
SM247I inch BMX.833" / 21.15 mm for older American bikes, BMX, early MTBs
SM2481 inch Standard.875" / 22.2 mmfits most bikes with threaded headsets.
SM2491 1/8 inch1.0" / 25.4 mmfits oversized forks with threaded headsets.