2 Syllables: SU
barrel, bestial, Bethel, Carol, Carroll, devil, Eccles, Ethel, ethyl, Federal, festal, gentle, Gerald, Harold, Hegel, Herald, kennel, kettle, level, levelled, levels, medal, meddle, Merrill, metal, methyl, mettle, nestle, nettle, pebble, pedal, peril, pestle, petal, phenol, rebel, restful, revel, revelled, revels, Reynolds, settle, special, speckled, sterile, treble, vessel, vestal, wrestle
3 Syllables: USU
ancestral, celestial, dishevelled, especial, Fitzgerald, imperil, imperilled, orchestral, successful, terrestrial, unsettled
4 Syllables: UUSU
accidental, continental, departmental, detrimental, elemental, fundamental, instrumental, monumental, Oriental, sentimental, transcendental, unsuccessful
5 Syllables: UUUSU
6 Syllables: UUUUSU
Found 75 words across 5 groupings. Skipped 22 excess words of a similar stem.