Or search: diam, gauge, grade, calibre, diameter, inferiority, superiority
2 Syllables: SU
bachelor, bachelor's, traveler
3 Syllables: SUU
amateur, flatterer, gatherer, janitor, Latimer, manager, massacre, traveller, vascular
4 Syllables: USUU
ambassador, coadjutor, diameter, examiner, parameter
6 Syllables: UUUSUU
cardiovascular

Found 18 words across 4 groupings. Skipped 12 excess words of a similar stem.