Don’t understand why your first section is shorter I have converted an extream 47 , two extream 18, two six 18, six25, ultimate 46 , and clx 27 all with no problem .
Surely if your top section of the pole is shorter it will work fine as that’s what you are doing by putting a spacer on that top section you are making it approx 60-70 mm up inside the base cap if that makes sense