3 Syllables: SUU
usually
4 Syllables: SUUU
barbarously, dangerously, dexterously, generously, ludicrously, rigorously, treacherously, vigorously
5 Syllables: USUUU
gratuitously
6 Syllables: UUSUUU
constitutionally, longitudinally

Found 12 words across 4 groupings.