Or search: radial, radiate, balanced, biradial, stellate, trigonal, bilateral, isosceles, cruciform, symmetric, harmonious, isobilateral, rhombohedral, proportionate, centrosymmetric
3 Syllables: SUU
chemical, clerical, ethical, festival, medical, metrical, plentiful, sceptical, skeptical, spherical, technical, vesicles
4 Syllables: USUU
electrical, heretical, hysterical, indelible, intestinal, numerical, poetical, receptacles
5 Syllables: UUSUU
academical, alphabetical, antithetical, arithmetical, asymmetrical, biochemical, dialectical, ecumenical, evangelical, geometrical, hypothetical, imperceptible, theoretical
6 Syllables: UUUSUU
infinitesimal

Found 34 words across 4 groupings. Skipped 2 excess words of a similar stem.