2 Syllables: SU
bubbling, bustling, covering, doubling, hovering, juggling, puzzling, smuggling, struggling, suffering, troubling
3 Syllables: SUU
blustering, budgeting, clustering, coloring, coverings, flourishing, fluttering, furnishing, mustering, muttering, nourishing, publishing, punishing, purchasing, servicing, shuddering, skirmishing, smothering, summoning, uttering
4 Syllables: USUU
Found 35 words across 3 groupings. Skipped 2 excess words of a similar stem.