Norma Bellino’s board at a 420-unit Manhattan co-op is dealing with a crafty serial subletter. It has fined the shareholder, but it seems his subletting business is too good to be thwarted by a monetary slap. What should the board do next? Phyllis Weisberg, a partner in Montgomery, McCracken, Walker & Rhoads, and Seth Sahr, a partner in Novitt, Sahr & Snow, team up to offer some strategies to undercut the subletter’s mini-business, ending it once and for all.