3 Syllables: SUU
Addison, Addison's, Africans, aliment, Alison, Allison, applicant, baptism, Fascism, garrison, Madison, talisman, Vatican
4 Syllables: USUU
5 Syllables: UUSUU
reestablishment

Found 17 words across 3 groupings. Skipped 4 excess words of a similar stem.