P6v7 - Activity start date is before project start date

In P6 7.0 - We created a second project after scrapping the first project. So the client decided they wanted historical activity in the second project and added an activity that has a start date that is prior to the project start date. They loaded the activity with resources and budgeted and actuals. Since the project start is way after the activity start (1 year), P6 seems to be jamming all the budgeted and actuals into a range of PS and DD. My question is whether it would be a good idea to change the project start at this point