lease conversion

When converting open leases I have a few questions:

1) Normalization will calculate based on the lease commencement date and termination date and the payment schedule for the lease term.  This means for normalization to calculate correctly, I will need to ensure the payment schedule is reflective of the lease term, which will then create payments for past periods.  What is the best practice approach to remove the payments from prior periods?

2) Operating Expense reconciliation - I believe in order for the operating expense calculation to work, the system will look at the payments made to the landlord for CAM, Insurance, and Taxes.  How will this work for historical payments where they were not be made out of Property Manager?