Hedge fund managers are increasingly nervous about getting a knock on the door from U.S. securities regulators now that a new rule requires them to register as investment advisers and provide lots of data about their inner workings as a result.Hundreds of large managers, which already employ sizable legal teams, took the mechanics of meeting the March 30 deadline in stride, industry consultants say.The cost of paying lawyers and adding compliance workers to ready for the new requirement, which was part of the Dodd-Frank financial reform act, generally proved most burdensome for funds with less than $500 million in assets. And all types of funds --large and small -- had to commit hundreds of hours going through the process of checking boxes and writing narratives.Now a far bigger concern for...