Previous solution:
lip, lips, lis, lisp, lop, lops, oil, oils, ops, poi, pois, pol, pols, polis, pos, psi, silo, sip, slip, slop, soil, sol, soli, sop, spoil
lip, lips, lis, lisp, lop, lops, oil, oils, ops, poi, pois, pol, pols, polis, pos, psi, silo, sip, slip, slop, soil, sol, soli, sop, spoil