3 Syllables: SUU
capital, Capitol, classical, graphical, Hannibal, magical, radical, tragical
4 Syllables: USUU
botanical, dynamical, fanatical, fantastical, grammatical, irascible, mechanical, theatrical, tyrannical
5 Syllables: UUSUU
biographical, enigmatical, geographical, mathematical, piratical, problematical, puritanical, topographical, typographical
6 Syllables: UUUSUU
ecclesiastical
7 Syllables: UUUUSUU
autobiographical

Found 28 words across 5 groupings. Skipped 3 excess words of a similar stem.