Or search: rim, mete, moho, bourn, brink, verge, bounds, bourne, fringe, margin, maximum, frontier, extremity, perimeter, periphery
2 Syllables: SU
boundaries, bounties, bounty, counties, county, downy, foundries, foundry, roundly, soundly
3 Syllables: USU
profoundly
5 Syllables: UUSUU
unaccountably

Found 12 words across 3 groupings.