Midyear RS enrollment. EMP-YTD-CONT

We are in the process of working on a conversion of additional employees (from one of our affliates) that will convert to Lawson mid year 2013.  This would include employees who are enrolled in spending accounts (RS plan type).  We are trying to figure out how to convert these records to bring in the employee's deductions that were already taken in their other payroll systems and subtract that from their annual election in order to determine how to calculate the remaining deductions based on the number of pay periods remaining for the year. 

1.)  What start date do we use on the plan? beginning of the year or first day of the first payroll after conversion.
2.)  What do we enter for BEN-COV-OPT?  26 payperiods or the number of payperiods left after conversion
3.)  What do we enter for BEN-PAY-RATE?  We'd like to enter the employees annual election since that field is sent onto our FSA administration vendor.  But should we just put the remaining amount (annual election - ytd deductions).

Has anyone done this before and used the EMP-YTD-CONT field and the PR797 that I have read about in Knowledge base?

Any help is much appreciated.