Or search: tapestry, complexity, involution, knottiness, trickiness, elaboration, complication
2 Syllables: SU
breakfast, deadliest, dexterous, exits, extras, headless, lettuce, necklace, nexus, plexus, readiest, reckless, redness, sexes, Texas, wreckage
3 Syllables: USU
correctness, directness, infectious, prospectus

Found 20 words across 2 groupings. Skipped 1 excess word of a similar stem.