When I change the Person Hours per Person Month field in Accounting Options, there is no change to the total schedule and effort for the project.  How can I adjust the estimate to reflect overtime?

The person hours/person month field was never intended to be used for performing time/effort tradeoffs.  For estimating purposes, SLIM-Estimate assumes that a FTE person is a FTE person, regardless of the number of hours in an effort month.  To account for overtime or unusual staffing situations, you should adjust the FTE (full-time equivalent) peak staffing level.  

For example, to reflect 10% overtime, you need a peak staff that is 1.1 times the current peak.  You can do this using the Control Panel peak staffing dial or by extending or shortening the Phase 3 schedule.

NOTE: if you are using a PI from your completed projects, you should only make this type of adjustment if your history does not include overtime.  It is usually better to be conservative in making adjustments as overtime hours are often less productive.  If the completed projects you used to derive a PI had a similar amount of overtime, it is already reflected in the PI and no adjustment is needed.