Center letter: u
Outer letter: a g h l m p
Answers (30):
  galumph
  alum
  glug
  glum
  gulag
  gull
  gulp
  haul
  hula
  hull
  hump
  humph
  laugh
  luau
  lull
  lulu
  lump
  maul
  mull
  mullah
  muumuu
  plug
  plum
  plump
  pull
  pulp
  puma
  pump
  pupa
  pupal