Or search: infix, felony, insert, bribery, conjoin, surgery, engraft, ingraft, grafting, barratry, autograft, homograft, allograft, xenograft, attachment
2 Syllables: SU
acid, affix, avid, Bassett, blasted, Catholic, classic, drafted, drastic, fasted, gastric, graphic, Hazlitt, lasted, magic, placid, plastic, tacit, traffic, tragic
3 Syllables: USU
bombastic, dynastic, elastic, engrafted, fantastic, geographic, gymnastic, monastic, sarcastic, scholastic, thoracic
4 Syllables: UUSU
demographic, ethnographic, inelastic, photographic, telegraphic, topographic
5 Syllables: UUUSU
ecclesiastic, enthusiastic

Found 39 words across 4 groupings. Skipped 6 excess words of a similar stem.