Or search: prudent, thrifty, heedful, cautious, diligent, studious, troubled, archaism, provident, unhurried, deliberate, elaborated, protective, archaicism, conscientious
2 Syllables: SU
aerial, Ariel, barrel, burial, Carol, Carroll, Gerald, Harold, Herald, Merrill, peril, prayerful, sterile
3 Syllables: USU
Fitzgerald, imperil, imperilled, malarial, terrestrial
4 Syllables: UUSU
secretarial

Found 19 words across 3 groupings. Skipped 4 excess words of a similar stem.