2 Syllables: SU
bubbling, bustling, covering, doubling, hovering, juggling, puzzling, smuggling, struggling, suffering, troubling
3 Syllables: SUU
blustering, clustering, coloring, coverings, fluttering, functioning, mustering, muttering, shuddering, smothering, uttering
4 Syllables: USUU
Found 26 words across 3 groupings. Skipped 1 excess word of a similar stem.