Schedule Performance Index in P6

I'm in the process of rebaselining my projects and our management decided to implement SPI with the new baseline. As the revised baseline should show SPI of 1.00 (earned = planned or whatever earned is planned), I made the SPI equal to 1.00 by using the  percent complete calculated from the Schedule percent complete column in the physical percent complete column (This makes my earned = planned and therefore SPI = 1.00). But in reality the physical percent complete is much lesser than the schedule percent complete. I'm not clear if to match these percent completes now (so that SPI becomes 1.00) and rebaseline the project and at the next month update reflect the actual physical percent complete and bring the SPI way less than 1.00 (may be 0.60). I assume this is not an intelligent strategy. Could anyone guide me through?

Thanks,

Mohan