State-Boston Retirement System will invest up to $280 million in hedge funds of funds to get closer to the $4 billion plans target allocation of between 5% and 7% of assets. The system is seeking managers, but each will run no more than $80 million, confirmed Robert Tierney, executive officer. Plan officials have not decided how many managers will be added. The plan has about $140 million invested in hedge funds. Funding will come from a general redistribution of assets. New England Pension Consultants is assisting.