have you considered importing a bunch of hours into the accrued, Carry-over, and annual hour limit fields for each employee? I was a bit surprised to find that these fields are stored in PR1_EmployeeMasterFile. I guess if they have a lot of turnover/new employees then that would add some time to setting up a new employee.
There is also a field in PR_26EmployeeBnfitAccruals that gets updated when you manually type information in those fields. I did a little testing and when doing data entry it does not appear to check that information so you might not have to import into that.